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V6-K

\vic,-t)ti>t lOM

No. 161. ISSUED MAY, 1903. Vol.

««s.^^

cSi

X -^ .JWDEXEO

HTPOW, I

'^ JOURNAL

OF THE

INSTITUTION OF

ELECTBIOAL ENGINEEBS,

LATB

W SOCIETY OF TELE6I(APH-EH6IHEERS AND ELECTKICIANS.

FOUNDED 1871. INCORPORATED 1883.

INCLUDING

ORIGINAL COMMUNICATIONS ON TELEGRAPHY AND
ELECTRICAL SCIENCE.

PUBLIBHSO UNDSB THK BUPSBVIBION OF THB EDITING OOMMITTBB.

AND EDITED BY

W. G. MCMILLAN, Secretary.

XonOon:
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JOURNAL

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THE NEW YORK
Founded 1871. Incorporated 1883.

Vol. 32. 1903.

139913R

ASTOR. LENOX AND
FOlWUAiiONS
1941 L

ff^ T<^T

The Three Hundred and Eighty-ninth Ordinary General
Meeting of the Institution was held at the Institution
of Civil Engineers, Great George Street, Westminster,
on Thursday evening, February 26th, 1903 — Mr. James
Swinburne, President, in the chair.

The minutes of the Ordinary General Meeting of February 12th
were, by permission of the meeting, taken as read, and signed by the
President.

The names of new candidates for election into the Institution were
also taken as read, and it was ordered that these names should be
suspended in the Library.

The following list of transfers was published as having been
approved by the Council : —

From the class of Associate Members to that of Members —

Sydney Evershed. I W. F. Stuart-Mcnteth.

Edgar Llewellyn Ingram. | Laurence Maxwell Waterhouse.

From the class of Associates to that of Members —

Frederick William Topping.

From the class of Associates to that of Associate Members —

Arnold Grant Livesay.
William Marsh.
Francis Samuel Miller.
Alexander Houston Weddell.

George Ernest Etlinger.
Archibald Ernest Grant.
Arthur Frederick Harris.
Leopold J. Harris.

From the class of Students to that of Associates —

Samuel Blackley. | Sydney Elliott Glendenning.

Mahmoud Samy.

Messrs. W. R. T. Cottrell and W. Nairn were appointed scrutineers
of the ballot for new members.

Donations were announced as having been received since the last
meeting to the Library from the Maschinenfabrik Oerlikon, and the
Relatives of the late A. T. Weightman ; to the Building Fund from

Vol. 82. 85

620 ^ STOTTNER: THE NERNST LAMP. ' [Feb. a6th,

Messrs. A. Eden, F. Heppenstall, H. W. Lee, A. P. Pyne, R. C. Quin,
D. C. Wardlaw, L. Wilson; and to the Benevolent Fund from
J. W. Fletcher, J. G. Wilson, and J. H. Woolliscroft, to whom the
thanks of the meeting were duly accorded.

The President : Mr. W. R. Cooper, who has been the Institution's
representative on the Committee of Science Abstracts^ has been elected
Secretary of the Physical Society, and therefore he can no longer
represent this Institution. Mr. Kingsbury has kindly consented to
take his place, but the Council particularly instructed me to mention
this matter to the meeting, because we feel that the Institution is very
much indebted to Mr. Cooper for the immense amount of hard work
he has done as editor in past days, and the work he has most recently
done as the most active member of the Committee.

At the last meeting I reminded members of the Institution that the
Council would be glad to receive any suggestions of names for the
candidature of the new Council. As I then explained, the Council do
not bind themselves in any way to nominate people so recommended,
but they will be very glad of any names suggested by members, and
they will be carefully considered.

I will now ask Mr. J. Stottner to read the paper in his name on the
Nernst Lamp. ^

*N^ THE NERNST LAMP.

By J. Stottner, Member.

Few inventions in electrical science have created greater expecta-
tions, excitement, and speculation than the Nef nst Lamp, and with few
have there been such immense difficulties in obtaining practical and
satisfactory results.

From the time of the earliest application of the Edison glow-lamp
attempts were made, first, to discover a substitute for the carbon
filament ; secondly, to avoid the necessity of evacuating and sealing
the globe ; and thirdly, in case of the filament giving out, to accomplish
its exchange without at the same time throwing away the body of the
lamp itself.

In 1877 Jablochkoff took out a patent for a lamp in which the
illuminating body consisted of kaolin and similar refractory earths,
which become conductors of electric current as soon as heated to a
certain temperature.

Partly on account of the very low efficiency, but more particularly
by reason of the necessity for very high-tension currents, this invention
— in common with all other attempts — proved a failure, until Professor
Walther Nernst came to the front with his lamp in the year 1898.

I have lately visited the extensive lamp works of the Allgemeine
Elektricitats-Gesellschaft, and will endeavour to make you acquainted
with the development of the Nernst lamp manufactured there from its
earliest stage up to its present design, for which purpose the A. E.G.
has bc#n kind enough to supply me with original samples of the lamp

1908.] STOTTNER: THE NERNST LAMP. 621

in its various stages of development and design. The filaments of all
these lamps are made of rare earths, principally of zirconia.

The earlier types of Nernst lamps had no automatic heating arrange-
ment, and the filament or glower, as our cousins in America call it, had
to be heated to the temperature required (on an average about 700" C.)
to make it a conductor, by means of a spirit lamp or match.

The very first lamp brought out was type No. i (Plate I.) with a
straight filament, the compensating resistance (or bolstering resistance as
it is termed on the Continent) of which, consisting of a fine platinum wire,
^was arranged in parallel with the filament at a distance of about ^ in.

In t3rpe No. ia (Plate I.) the filament was bent in a similar manner to
that of the first Edison bamboo carbon incandescent lamp, and was in
the shape of a horseshoe. The burner of this lamp could be exchanged.

The bulb was open in order to facilitate artificial heating of the
filament, as mentioned before. The bolstering resistance, to which I
shall refer again later, consisted of fine platinum wire wound round
two small porcelain tubes, and was exposed to the air to obtain a better
cooling effect.

The filament in t3rpe No. 2 (Plate I.) was exactly the same as in
No. IA, but the bolstering resistance was wound on one small porcelain
tube only, and partly covered with kaolin.

In type No. 3 (Plate I.) the resistance consisted of thin iron wire wound
on a very small kaolin tube, which was sealed and enclosed in a<glass tube.
This tube was evacuated and afterwards filled with hydrogen gas. All
these models, however, proved unsatisfactory, and platinum wire was
again resorted to as a bolstering resistance, as type No. 4 (Plate I.) shows.

In this lamp the large loop is the resistance, which was prepared in
almost exactly the same manner as the heater of the present day, a
very fine platinum wire being wound in a spiral on a thin kaolin tube
and then steeped in a solution containing kaolin. The small loop is the
filament. It will be noticed that in this lamp filament and resistance
are fixed for the first time on a porcelain base. This shape of resistance
was in use for a considerable time and will be seen again in the later types.

The trouble of lighting the lamps by means of a spirit lamp or match,
however, prevented their being brought into general use. They were
exhibited for the first time in public in conjunction with some auto-
matically-heated lamps at the Paris Exhibition of 1900, where the
patentees, the Allgemeine Elcktricitats-Gesellschaft, of Berlin, had a
magnificent pavilion lighted entirely by Nernst lamps. At this time
the difficulties had by no means been overcome, but seemed rather
only to have commenced, and it was found absolutely necessary to
cfiEect the heating of the filament automatically in order to bring the
lamp into practical use.

In type No. 5 (Plate I.) the automatic heater will be observed for the
first time. The filament in this type was again a straight rod, placed
horizontally to the base of the lamp. The thick porcelain tube next to
it contained the heating wire, and the smaller tube the bolstering
resistance. Both filament and bolstering resistance in this lamp could
be exchanged. The automatic cut-out was embedded in the socket.
It will be observed that the magnet had great masses of iron and a

522 STOTTNEK: THE NERNST LAMP. [Feb. 26th,

heavy armature, in consequence of which a ;»reat deal of energy was
required to actuate it.

In type No. 6 (Plate I.) we see for the first time a heater in the form
of a coil, in the centre of which the filament is placed. The heating coil
was prepared in a similar manner to that in type No. 4, but mounted
together with the filament on a somewhat larger base, and could be
easily exchanged. The bolstering resistance was the same as in type
No. 3 and could be exchanged, but was firmly fixed to the socket.
The magnet was identical with that of type No. 5, and the glass bulb
similar to that of an ordinary incandescent lamp.

Type No. 7 (Plate I.) is very similar to No. 6. This lamp was
designed for 220 volts. The filament could not be arranged in a
horizontal position on account of its length, and therefore both filament
and heater were mounted vertically to the base.

A great improvement is shown in type No. 8 (Plate I.). Here for
the first time will be observed in the bolstering resistance spirals of
thin iron wire suspended free of the carrier.

Type No. 9 (Plate II.) was a departure from the usual practice, in
which a loop filament was again used and a magnetic cut-out placed
alongside of the bolstering resistance instead of being embedded in the
socket.

Up to this time the lamps had been manufactured only in small
numbers, but types Nos. 10, 11, 12 (Plate II.) and 13 (Plate III.) were
now designed and for the first time produced in considerable quantities.
These lamps show two distinct forms, the *' A " type with large body
and globe, and the "B" type with small round globe and body so
ananged that it could be used in an ordinary Ekiison screw lamp socket.

The " B " lamps, types 10 and 1 1 were manufactured for an energy
consumption of 40 and 80 watts and potentials of no and 220 volts
respectively. The bolstering resistance in these types again consisted
of platinum wire as in type No. 4. As on account of their small size
it was impossible to combine these filaments with a modern iron
resistance they were all arranged in a horizontal position. The heating
spirals were mounted firmly on the porcelain baseplate, which could be
easily exchanged. In these lamps the magnet of the automatic cut-out
received its final shape, being marked by very small masses of iron
and a very light spring, and in consequence thereof by a very small loss
of energy. The ** A " lamps were for higher currents up to i ampere,
and had to be separately connected in a similar manner to that in
which an arc lamp is connected.

Types 12 and 13 were designed for an energy consumption of
100 and 200 watts with a corresponding lighting capacity of 65 and
130 standard candle-power respectively. In this type the burner, as
well as the bolstering resistance, could be independently exchanged.
These lamps were made for no and 220 volts. As opposed to the
" B " lamp, the filament and the heating coil were arranged in a
vertical position. The design of the magnets of the automati^JuTouts
was exactly the same as that in the " B " lamps. 'rjMrmetal cap
covering the resistance was provided with ventilatin^jjflots, so that the
bolstering resistance was cooled by the circulation^

(Showing Kemsl Lainj\ Types s-8}

Plate II.
(Showing Nernst Lamp, Types 9-12, and 24.)

Plate III.
(Showing Nernst Lamp, Types 13 and 25.)

VAhh\hh.hhH\\hh%\SShVAHHVA\hMJ^WAfJ

1903.] STOTTNER: THE NERNST LAMP. 523

Types Nos. 14, 15, 16, 17 and 17A show the development of the
Nernst lamp as a candle lamp for chandeliers, etc. These lamps do
not deviate materially from those described up to now, but correspond
with the ordinary lamps in each successive stage of development.

In Nos. 18, 19 and 20, the gradual reduction of the iron masses
in the magnet will be noticed. The first magnet weighs about three
times as much as those in use at the present day.

Nos. 21, 22 and 23 (Plate III.) show experiments in disconnecting
the heater by other means than that of an electromagnetic cut-out.

Sketches A, B and C (Plate IV.) show the corresponding diagrams of
current in these devices. The springs of compound metal bend to one
side as soon as heated. These inventions, however, did not come into
practical use and, indeed, never left the laboratory. I merely mention
them to show that all kinds of researches wxre made with the object of
improving the details of Nernst lamps.

Nos. 24 (Plate II.) and 25 (Plate III.) show the latest patterns of
Nernst lamps, as now in use by the million.

No. 24 is the A type lamp. The burners are manufactured for
I ampere up to 250 volts, and for i ampere, only, from 200 up to 250
volts. The metal hood is furnished with metal combs of thin sheet
copper in the inner cover, for the purpose of cooling the bolstering
resistance. Between this inner tube and the outer mantle are a number
of tubes for ventilation purposes and to facilitate the radiation of heat.

The replacing and fixing of burners is a very simple manipulation,
and can be effected by any unskilled person.

For customers who have A lamps of the old type we have designed
special adapters, so that the new burners can be used on such lamps.

No. 25 (Plate III.) is the latest B type lamp, which is manufactured
for i and i ampere up to 150 volts, and for J ampere up to 250 volts.

The replacement, etc., of burners is quite as simple as in the case
of the A type lamp.

Nos. 26 to 36 are various bolstering resistances, all made of iron
wire, sealed in glass globes which have been evacuated and afterwards
filled with hydrogen. Iron wire is used on account of its high
temperature correction, which makes it particularly suitable, as, for
instance, should the current increase 5 per cent, the resistance of the
iron wire increases about 75 per cent., thus preventing the destruction
of the filament. The increase of resistance in the iron wire is not
proportionate throughout, and it is therefore necessary that the sectional
area should be chosen with a view to heating the wire to a critical
temperature by the current with which the lamp is intended to burn,
in order to arrive at the above-mentioned result, i.e., the balancing
of current by resistance.

Nos. 37 and 38 show filaments which have burned 1,400 and 1,600
hours respectively. Unfortunately No. 37 is broken, but from No. 38 it
can be easily seen that the filament has become crystallised. It is also
black throughout ; this discoloration starts at the negative pole and
gradually extends over the whole filament. The precise cause of this
crystallisation and blackening is not at present known, but we presume
that it is due to electrolysis.

524 STOTTNER: THE NERNST LAMP. [Feb. 26th,

As to the efficiency and life of the Nernst lamp, I refer to the table
of tests made at the Physikalische Technische Reich sanstalt at
Charlottenburg.

A number of lamps have been under test at the Electrical Testing
and Standardising Institution at Faraday House, London, since the
middle of December. The results, however, are still outstanding.

A great many errors in the treatment of Nernst lamps are committed,
in consequence whereof numerous complaints of short life, etc., are
lodged with the suppliers ; but if instructions are carefully followed a
life of about 300 to 400 hours — ^as practical results show — may be
expected. One great mistake generally made is that the current is sent
through the lamps in the opposite direction to that intended, particularly
in the " B *' type lamp. Another mistake is to overrun the lamps, as
the surplus current is then taken up by the bolstering resistance and
practically the light is not in the least increased.

On the Continent the screw holder is in almost universal use, and
the standard rule is to make the centre contact minus ; it is therefore
immaterial how frequently the lamps are taken out of their holders, as
they always come back to their proper position. With bayonet lamps
it is different : the poles can be easily changed by inserting the lamps
the wrong way, and to prevent this the A. E.G. have designed a tool
to cut out a slot, and have provided the porcelain socket of the lamp
with a third pin, so that it is impossible to get the lamps into the
holders the wrong way.

To determine the polarity on bayonet sockets special pole-finders
are supplied, the negative pole being invariably indicated by the red
appearance of the solution.

I have studied the principles and designs of the Nernst lamps
manufactured in the United States, and think that we here in the Old
World may pride ourselves on being at least as up-to-date as our
American cousins.

Mr. Drake. Mr. B. M. DRAKE : We are indebted to Mr. Stottner for kindly

giving us the history of the evolution of the Nernst Lamp, as wd^-ked
out by the Allgemeine Elektricitats-Gesellschaft, of BerHn, and it may
be of interest to compare what has been going on in this country in
connection with the same problem. As you may know, when this
invention was first brought to public notice, attempts were made at
a meeting at Berlin of the holders of all the patents of Nernst for the
world to arrange for an interchange of experience by which the lamp
might be brought to perfection in less time than would be possible if
each worked on his own account. At that meeting, which Mr.
Swinburne and I attended on behalf of the Nernst Electric Light
Company, there were present Mr. Westinghouse, the AUgemeine
Elektricitats-Gesellschaft, and Messrs. Ganz. Two days were spent in
discussing the invention, which was regarded as marking a new era.
There was a serious discussion as to the result on the electrical industry
when the lamp should make its appearance. One influential member
said there was no doubt that if these lamps were put upon the market
indiscriminately the supply companies' business throughout the world

1908.]

THE NERNST LAMP: DISCUSSION.

525

would be affected to a serious extent : the companies would suddenly Mr. Drake,
find that their output was halved, with the result that it would be
impossible for them to pay dividends for the year. It was further
stated that it would be impossible for the wiring contractors, however
numerous they might be, to wire the additional houses which would at
once rush for the electric light, owing to the fact that the cost of
lighting would be halved. All sorts of methods were suggested as to
how the lamp should be put upon the market gradually, so as not to
upset the electrical industry. These hours of discussion, however,
were somewhat wasted, for providence looked after the electrical
industry. As soon as we had finished our discussion, we all went home
and discovered that none of us could make the lamp at all. Un-
fortunately, owing to international jealousy, we were unable to come
to any arrangement by which we could arrange an interchange of
improvements, and the result was that each tried to work out the lamp
for himself. There are on the table specimens showing the progress
of the Nernst lamp as we designed it in England. Unfortunately we
had not the unbounded resources of the AUgemeine Elektricitiits-
Gesellschaf t, and we were blessed with a boisterous set of shareholders,
who would not leave us alone, besides which we had to manufacture
out of England. Had it not been for these drawbacks I think we
should have put our lamp on the market as soon as, if not sooner than,
the AUgemeine Elektricitkts-Gesellschaft. Some of the results which
we were able to produce are shown in the curves exhibited. These
are the mean results of a number of tests which were made ; and you
will see from the Curve Fig. A that we were able to produce lamps which

too £00 JOO

400 500 600 TOO
Life in Hours

Fig. a.

&00 900 IjOOO

started at 20 candle-power, and after 800 hours had only dropped to
16*5. The tests were very carefully taken, and will compare favourably
with the results obtained by any carbon lamp which has ever been
made : the average watts being 27 per candle throughout the whole
period. The next diagram (Fig. B) shows the drop in candle-
power of large lamps of 200 volts, starting at 130 candle-power and
ending at about 80, with a mean efficiency of 2*3 watts in 700 hours.

526

Mr. Drake. i^q

i 60

STOTTNER : THE NERXST LAMP. [Feb, 26th,

— .

too

zoo

300 ^900

Life in Hours

Fig. B.

500

600

700

the Curve Fig. C shows the rapid way in which the volts absorbed
by the resistance increase with the smallest increase of current. The
result is that when these series resistances are used with Nernst lamps

you get a more regular candle-
power with variations of volt-
age than with the carbon lamp.
The Curve Fig. D shows the
percentage variation of candle-
power of the carbon lamp and
the Nernst lamp, with different
voltages. It will be seen from
this that in the Nernst lamp
the candle-power does not in-
crease to anything like the
same extent as in the carbon
lamp. The carbon lamp, with
a rise from loo to 115 volts,
has increased in candle-power
in a ratio of 100 to 230,
whereas the Nernst lamp under
the same increase of pressure
has only increased to 130. The
iron resistance may be looked
upon as one of the turning
points in the Nernst lamp, and
it will be used to advantage
in series with the ordinary
carbon lamp on traction cir-
cuits where the voltage is not
very regular. In Mr. Stottner's
paper there are one or two
points, probably slips, to which perhaps he will not mind my referring.
Near the top of page 521 he talks of the resistance being arranged
in parallel with the 61ament ; I think he means in series.

o-e

o^ 06 o-e

Current in Amperes
Fig. C.

10 IE

1903.]

THE NERNST LAMP: DISCUSSION.

627

Mr. Stottxer : As a matter of fact the resistance and filament are Mr.
arranged in parallel, but electrically, of course, they are connected in ^'*^""*''-
series.

Mr. Drake : The next point is with regard to the claim of the Mr. Drake.
Allgemeine Elektricitats-Gesellschaft to be the first to show an
automatic lamp. Mr. Swinburne will bear me out that the lamp
originally shown at the Society of Arts, which is on the table, is
automatic, the heating hood being lifted by a powerful magnet away
from the glower. Also automatic lamps made by Ganz were shown
in 1899, at the Royal Society. The Ganz lamps are also on the table
for the inspection of members who would like to see them. The lamps
whicli are alight now are
some of the products of *3^or
the Ncrnst Company. I
would ask Mr. Stottner
to look at one of them
with duplex glowers, be-
cause the Allgemeine
Elektricitats-Gesellschaft
might do well to adopt
it. We have not seen any
of their make arranged
in this way, and for street
lighting they are very
suitable because a single
glower hardly gives
enough light! for street
purposes, whereas the
two just suffice. The
Westinghouse Company
have not up to the pre-
sent produced a con-
tinuous-current lamp, Mr.
Westinghouse having
concentrated his attention
on the alternating lamps,
and, curiously enough,
we found the alternating

a much more difficult problem than the continuous. The Westing-
house lamps, which are also on the table, consist of a large number
of small glowers; I presume he found difficulty in baking the
large glowers, which is a difficult problem, and required a consider-
able time to solve. Mr. Westinghouse fuses the conductors into the
ends of his glowers in a way which is different fropi that adopted by
others, which is apparently better for alternating glowers. Messrs.
Ganz started very energetically on the Nernst lamp, and the specimens
shown on the table are very creditable examples, considering the
time at which they were made. But as soon as they found the
enormous outlay which would be necessary in order to bring the
Nernst lamp into a practical state, they apparently got frightened and

3£> 100 loa 110 //5
PercenCoLge of Normal L f^iMSure

Fig. D.

628 STOTTNER: THE NERNST LAMP. [Feb. 26th,

Mr. Drake. yqH it alone altogether. We, for commercial and company reasons,
have made arrangements with the Allgemeine to manufacture for our
districts, and therefore the Allgemeine must be gii^en the full credit for
being the first in the world to put the Nernst electric lamp on the
market in a condition in which it will meet commercial requirements.

Hammond. ^^* ^' Hammoxd : I was hoping that the general body of the

members would take the opportunity presented to them of having
these leading experts on the Nernst lamp in the same room with them,
to do a little heckling. And I am surprised at the backwardness
of those who, I am sure, have so many questions to ask. Possibly,
however, they will come on a little later in the evening. With regard to
my attitude towards the lamp — and I think possibly it is the attitude of
most of us — I feel that the ideas which were prevalent originally that the
. introduction of a lamp of very much higher efficiency would greatly
damage our industry, arc absolutely chimerical. The more cheaply we
can utilise the energy which we produce, the more cheaply we can
give light, and the more important will our industry grow. I had the
pleasure of visiting the Buffalo Exhibition, and I was very much struck
with the splendid exhibit of George Westinghouse ; I spent more time
in that portion of the exhibition than in any other portion, and I came
back to England feeling that there was no reason why we should not
start in this country street-lighting by means of Nernst lamps. Now,
I am much interested, as I am sure you all must be, to hear from
Mr. Stottner that the whole question of the efficiency and life of the
lamp has been settled by the tests made at the Physikalische Tech-
nische Reichsanstalt of Charlottenburg. You tell that to a town
councillor, and unless he can get his friends to vote him a sufficient
sum to go and visit these works himself, he wants the efficiency
demonstrated on the spot. I therefore undertook for my friends and
paymasters at Hackney to carry out a mile of street lighting on the
Nernst system ; and I was anxious to do so, not that I disregarded the
wonderful results that were achieved by the Physikalische Technische
Reichsanstalt of Charlottenburg, but because I felt that if the Nernst
lamp was going to supersede the old-fashioned lighting which prevails
in the streets of the United Kingdom, it would do so after practical
results in the streets, rather than in the laboratory of the Physikalische
Technische Reichsanstalt, that very excellent institution at Charlotten-
burg. Now, we have got a mile of street lighted, and in due course I
was called upon, in conjunction with the resident electrical engineer,
Mr. L. L. Robinson, to give a report as to the extension of the lighting
to the whole of the 125 miles of streets in Hackney. Well, of course,
as a consulting engineer always anxious to extend the scope of one's
work, I was naturally tempted to say. Go in and light the whole mileage.
But with due regard to a character which it is so difficult in these days
to keep, I felt that it would be well that I should lay before the
councillors of Hackney some actual results. And I, knowing their
attitude, did not drown them with those achieved by the Physikalische
Technische Reichsanstalt of Charlottenburg. I had to tell them how
much per annum each lamp was likely to cost them on the basis of the
life — or want of life, because you cannot tell the length of life until it

1908.] THE NERNST LAMP : DISCUSSION. 529

is dead — of those that had already been put up. You see, gentlemen, Mr
how far removed from science one sometimes has to be. And finally
I laid before them this report. It is not all Physikalische Technische
Reichsanstalt ; there are one or two other things in it, and I shall have
very much pleasure in presenting it to the Institjition, which will be
even a greater pleasure than reading it all through to you to-night. So
that if it be deemed worthy, or if any portion of it be deemed worthy
by the Editing Committee to constitute a sort of supplement to the
scientific contribution that has been so ably made to-night, it is at the
disposal of that Committee. But what I found was this : — First, that
of these lamps, which were placed roughly about 42, 43, 45 yards apart,
40 lamps going to the mile, the first one finished his life in 130 hours.
The cause of this failure was failure of flex connected to the glower.
Now I am sure you will all agree with me that having a gentleman
before us who is so well acquainted with the reason of flexes failing,
he will be able to give us some idea of how we shall be able to arrange
that in future the flexes connected with the glower do not fail. I may
say that by the commercial arrangement which has been referred to by
Mr. Drake, all the lamps were obtained from the Electrical Company,
and it is therefore for Mr. Stottner to tell us why in No. i lamp, which
we thought was going to last so efficiently for 800 hours, the flex failed
in 130 hours. We had, of course, to fix another lamp in its place, and
the second lamp, up to the time of the making of these tests, lasted 930
hours, and he is going on lasting. With regard to the No. 2 lamp in
the street, it was going merrily on after 542 hours. No. 3 lamp had to
have a good deal of attention paid to it We had men carefully
patrolling this mile the whole time, so as to be able to get accurate
results. The first lamp fixed on No. 3 post disappeared in 34 hours
because there was a fracture of the glower at bottom contact ; and
that is the constant fault we have discovered, at all events at Hackney.
This report, I may say, is dated February 2nd of this year. The
second lamp fixed on No. 3 post gave a life of 96 hours, and in that,
again, there was fracture of glower at bottom contact. The third
lamp put in there lasted 453 hours, and died from failure of heating-
coil due to faulty action of auto-cutout. We put in a fourth, and that
disappeared in 150 hours ; he went back to the old complaint, and, like
his grandfather and his greatgrandfather before him, he died from
fracture of glower at bottom contact. And the fifth lamp took up the
running, and at the time of the test was 241 hours old. I am not going
to weary you by reading the history of the whole of them, but the
awkward thing is this, that the lives vary considerably. It reminds you
of a chapter in Genesis, because some of them lived to such an
advanced age ; thej' vary from 1,070 hours and still young, to 15 hours
and dead and gone. And the 15-hour one died from failure of the
heating coil. We put another one in his place, who only attained
a life of 30 hours, and he died from failure of the heating-coil. Well
now, these figures, which I think you may take as absolutely reliable,
can be summarised as follows. The total number of burners tested to
full life was 67. The total burner hours, including only such burners
as failed, was 20,499 > ^^® average life of the burners, that is to say the

Hammond.

530

STOTTNER : THE NERNST LAMP.

[Feb. 26th,

Mr.
Hammond.

Professor
Ayrton.

dead ones (as we cannot get their average lives till they die), was 305
hours. Taking that as the basis of the life, I was compelled to get
these results out in advising as to whether I could conscientiously
recommend the Vestry to permit me to light the whole 125 miles of
streets by this means. We found that these lamps gave their 80
candle-power pretty consistently with the half an ampere on a 240- volt
circuit. I will take the working cost of 3,940 hours per annum,
debiting the current at l}d. — as a matter of fact it was I'yd. — debiting
them with renewals on the basis of the life shown by these experiments,
11*5 burners and one resistance and one globe, sundry stores and
labour. We thus get a certain net cost of working. The lanips then
have to be debited with the interest on the repayment of capital on the
basis of a ten years' loan at 3^ per cent, plus 8J per cent., equals 12 per
cent., a total sum of £^ 17s. 9d. per annum. Well now, in this country
the town councillors [of course not the ekctrical engineers (nothing in
the way of electricity is too dear to them), who may consider that
£$ 17s. 9d. would be a very proper expenditure per lamp for the sake
of having the Nernst lamp] think that that figure does not compare
favourably with the price which would hold at all events if the lamps
lasted as long as they do at Charlottenburg. I think we may ask Mr.
Stottner to help us in his reply to explain the causes of these failures,
because, speaking for myself as representing Hackney, I should be
only too delighted if these failures did not occur, and if the whole of
those 125 miles of streets were lighted with that lamp. And I think
that what applies to Hackney applies also through the country. We
cannot do with a lamp that has not a uniform life. In the early days
of the incandescent lamp, as we recollect, and our President will
remember one or two episodes with regard to it, the difficulty was not
that of making the lamp — our President made them in large quantities
— but the difficulty was that of getting them uniform. If you attempt
to put in lamps for street lighting some of which last 15 hours, and
some of which last 1,000 hours, it puzzles even a consulting engineer,
electrical as he may be, or otherwise, to determine the proper number
of renewals which he has to provide for ; because you cannot have
street lighting with certain lamps out and certain lamps in. The disin-
clination to push the Nernst lamp throughout the country is, I think,
largely due to its not being a truth-teller ; he does not always do what
his brother did yesterday. If we can get all the members of the family
to live the same life, even if it is not 800 hours, but 790, or 665, we
shall have attained very much nearer to its adoption than we have got
to-day.

Professor W. E. Ayrton, F.R.S. : I will only say one word, as it is
getting very late. I want to ask one question. Mr. Hammond has
dealt in a very facetious way with the attempt to light a street in
Hackney with the Nernst lamp ; but the point I wish to "deal with is
the one which Mr. Hammond has passed over so easily. He has only
dealt with failure arising from mechanical causes. No doubt those are
very serious for any practical system of lighting, but with improved
manufacture those failures can be overcome. But what I want to deal
with is the point which he passed over, namely, that these lamps do

1903.] THE NERNST LAMP: DISCUSSION. 631

give the 8o-candle-power light during the whole of their life. Now, Professor
my experience has been the opposite. It is a small experience, I grant "'

as far as lamps that I have used myself is>* concerned, but it is not a
small one if one looks at the Nernst lamps in shops and various other
places. And I would like to ask one of the numerous experts whom
"we have the pleasure of seeing here to-night on the subject of this
Nernst lamp, why the practical Nernst lamp does not follow any such
curve as shown in those diagrams. If the English Company were able
some time ago, as I understood Mr. Drake to say, to make Nernst
lamps which in 800 hours only fell from 19 candles to 16*5, why is it
that such lamps are not made and sold at the present day ? One other
question is, what is the cause of the falling off of the light of a Nernst
lamp ? I should like to know that very much. One knows that in the
case of the ordinary glow lamp it is due to a change in the surface of
the carbon filaments, by which it becomes a worse radiator of light,
and sends off the energy at a lower temperature. Does anything like
that occur to some extent on the Nernst filament ? Does its surface
change so that as it ages, say after 100 or 200 hours, it gives off energy at
a lower temperature ? Or what is it that happens ? Is it a change in
its nature which causes what must be the common experience of many
present, namely, the light to fail and not to remain, as I wish it did,
f oDowing the curve such as Mr. Drake has indicated ?

Mr. M. Solomon : I should like to add a few remarks to what has Mr.
already been said on the Nernst lamp, especially with reference to
Professor Ayrton's comments on the candle-power cur\xs shown by
Mr. Drake. Of course one does not always get such good results as
these, especially so good as those in the curve in Fig. A, which repre-
sents the mean result of tests on three lamps. That curve does drop a
certain amount, and the curve in Fig. B drops rather more, but perhaps
the average curve obtained with the commercial lamp of to-day drops
more than either. Still I would point out one fact with reference to
judging the performance of the lamps by those which one sees burning
in shops, namely that in the first part of the curve there is a very
marked drop in candle-power from about 130 to no. My experience
is that there is always a drop corresponding to that, though not
perhaps always so great, and sometimes a little greater. The result is
that after the first 50 hours the light from a Nernst lamp seems to
change a good deal in colour on account of this first drop. The light
is a very white one at first and remains white during the whole life,
but one notices a considerable difference in shade if two lamps, one
new and one 50 hours old, are observed side by side. But after that
drop the candle-power remains fairly steady, as shown by the curve,
which is quite a typical one. When the curve drops off sharply
towards the end it is a sign that the lamp is about to fail.

It is interesting to note in connection with the curves in Figs. C and
D showing the behaviour of the iron resistance and the increase of
candle-power with increase of voltage, that one may actually lose in
efficiency by over-running a Nernst lamp. The reason is obvious when
you think of it, for if the lamp is over-run by 15 per cent, the candle-
power is only increased very slightly, but the volts taken by the

682

STOTTNER : THE NERNST LAMP.

tFeb. 26th,

Mr.

Solomon.

resistance are increased by a very great amount. The result is that
the percentage of the total volts, and therefore the percentage of the
total watts, absorbed by the* resistance is very much greater, and the
actual over-all efficiency of the lamp I have found usually falls when
the potential di£Ference at the terminals is increased. This is clearly
shown by the curves in Fig. E, which are for a half -ampere 200- volt
Nernst lamp. It will be noticed that the total watts per candle increase
slightly when the supply pressure is raised above the normal. There-
fore it is of course not only inadvisable but useless to try to get more
out of a Nernst lamp by over-running it. The curves for the iron
resistance have already been referred to by Mr. Drake, and also by Mr.
Swinburne in his presidential address ; they are very remarkable
curves, and the Nernst lamp, by leading to the invention of this iron
resistance, has given us what is in some ways a new piece of electrical
apparatus, which may be of great use in other classes of work. One

ISO

I90 200 aio 2Z0 e30

/bCenC/ciC Difference At Lcunp dermindiis in VoUs
Fig. E.

can, for example, use these resistances in series with an arc, and one
can get certain results by so doing which it is very difficult to obtain in
other ways. If a resistance of this sort is used it is possible to run an
arc with a very low current more steadily, and on a circuit of lower
voltage than is possible with an ordinary resistance. I have tried this
experiment, and succeeded to a certain extent, though there are certain
difficulties in the way. The explanation is clear if one considers the
curves for the arc which were first published by M. Blondel, and which
Mrs. Ayrton has made familiar to us all. The resistances can also be
used with ordinary glow lamps, and it might be a great advantage to
use them with the standard incandescent lamp described by Professor
Fleming. It would do away with the objection which must militate
against the use of a carbon lamp as a standard, namely, that the candle-
power is so sensitive to the voltage ; by using a resistance of this sort
one gets a curve similar to that for the Nernst lamp in Fig. D, and one

1908.]

THE NERNST LAMP : DISCUSSION.

688

Solomon.

Mr.

Vignoles.

can get much better working results for practical purposes in this way Mr.
and can dispense with the trouble of having to use a potentiometer. °"**"*

I should like to refer to one other matter. Mr. Drake called your
attention to the two-glower lamp which is shown on the table : there is
also exhibited another two-glower lamp in which the glowers are
arranged in series, so that it runs direct on a 400- or 500-volt circuit.
This lamp has been run and tested, and it worked extremely
satisfactorily on a 500-volt circuit.

Professor Ayrton : Will Mr. Solomon add, to the interesting in- Professor
formation he has given, one fact ? The lower curve is of such ^y^""-
enormous importance that I wish to ask this question. It is a ciu-ve
showing that under some conditions the Nernst lamps are as good
as far as their life is concerned, as a very good ordinary carbon glow
lamp, but giving a higher efficiency. I want to ask, did you require
much more heating to make that particular Nernst filament glow?
Did you expend much more power in your heating coil than you do
with an ordinary commercial lamp so as to start the glowing of the
filaments which were used in those six lamps ?

Mr. Solomon : In answer to Professor Ayrton, I may say that those Mr.
lamps were perfectly ordinary Nernst lamps, and had exactly the same
heating coil as the commercial lamps which the Nernst Electric Light,
Ltd., were then making. This coil took practically the same current
as the modern commercial lamp made by the A.E.G.

Mr. E. B. Vignoles : I want to ask one question with regard to a
point which has not yet been touched upon this evening. It has regard
to the liability to damage due to variations in the voltage on the lamp
terminals. With the instructions which the Allgemeine Elektricitats-
Gesellschaft send out with their lamps is a statement to the effect that
the voltage on the lamps must be kept steady. My experience of these
lamps is limited, but I have found that with the ordinary, more or less
unsteady, voltage which is provided in my factory for the purposes of
lighting the lamps gave out in a very short time. Will Mr. Stottner
tell us to what extent the voltage may be allowed to vary with impunity,
and whether the rapidity of variation in the voltage has any effect on
the lamps or their resistances ? For instance, if I put the lamp on to a
dynamo driven by a gas engine which is varying frequently to the
extent of, say, 5 per cent, of its voltage, is the lamp likely to give out
quickly? It would appear from the breakdowns to which I call
attention that the fine iron wire is run at such a temperature that quite
moderate variations of voltage are sufficient to destroy it : and this
defect seems serious, in view of the fact that on any supply a temporary
rise of voltage is liable to occur.

Mr. A. A. C. SwiNTON : Another point with regard to which I think
it would be desirable to have further information is, the comparative
results that can be obtained with these lamps with continuous currents,
and with alternating currents. Personally, I have had a satisfactory
experience of their working with continuous currents in my office.
But in other places where I have had them tried and the current is
alternating, with a frequency of 80, the results have not been good at
all. Now, what I am anxious to know is this : Is this difference in

Mr.

Swintofi.

534 SfOTTNER: THE NERNST LAMP. [Feb. 26th,

swinton. result due to something inherent in the alternating current, or is it due
to what I think may possibly have been the fact, that with the
alternating current the voltage was not quite as steady ? I have my
office in Victoria Street, and I am supplied by the Westminster
Company, whose voltage is exceedingly steady, but I rather fancy that
there is something in alternating current which does not agree with
these lamps. That is only surmise on my part, however. With regard
to the falling off of the candle-power, the scientific aspect of the
question has been mentioned by Professor Ayrton. Now the filaments
of these lamps are made of materials the same as, or analogous to, those
used for incandescent gas mantles ; and it is well known to everybody
who uses incandescent gas mantles that these mantles fall off very
much in candle-power in course of time. I think the reason they fall
off is also known. I believe I am right in saying that the Welsbach
mixture of which these mantles arc composed is about 99 per cent, of
oxide of thorium and i per cent, of oxide of cerium, and it makes an
enormous difference what the exact proportion of cerium is ; i per
cent, makes all the difference in the world. I understand that the
cerium is more volatile than the thorium, and that consequently after
a time the cerium has a tendency to disappear. In fact, I believe that
the ordinary practice of the manufacturers of incandescent gas mantles
is to put in too much cerium to begin with, so that really you get the
best effect at about the middle of the life of the mantle. At first sight
one might think that a similar effect may be the reason for the falling off
in the candle-powder of these Nernst lamps, but I wish to put forward
a reason which I think makes that exceedingly doubtful. About two
or three years ago I made some experiments, which were communicated
to the Royal Society, upon the luminosity of incandescent mantles ; the
mantles were not exactly like those made for ordinary use, but were
made very thick, though manufactured in the same way. I heated them
to bright incandescence by bombarding them with cathode rays in a
vacuum tube ; and I found that whereas in a Bunsen gas burner a
mantle of purt oxide of thorium gives only something like one-eleventh
of the light that is got with a mantle made of the Welsbach mixture,
pure oxide of thorium when bombarded with cathode rays gave practi-
cally the same amount of light as the Welsbach mixture. There was a
slight difference, but the difference was estimated at not more than 5 per
cent. Wc had a patchwork mantle made, half of one and half of the
other, and when we bombarded it equally all over we could barely
see that one half was brighter than the other. That goes against the
theory of evaporation and consequent alteration in the mixture being
the cause of the falling off in the light when the heating is effected by
anything else than a gas flame, and I am inclined to suggest that it is
probably a change in resistance more than anything else that causes
the Hght to diminish ; that the electrical efficiency remains more or
less the same, but that the current goes down, and with it the light.
I think this is a most interesting subject, and I have a great belief
in the future of these lamps provided that, as I have no doubt is the
case, the defects mentioned by Mr. Hammond can be got over by
improved manufacture. Further, I think that this question of improved

1903.]

THE NERNST LAMP: DISCUSSION.

585

lamps is one of the most important subjects which can be discussed by Mr.
this Institution. ^'^°*°°-

Sir Henry Mange : With reference to the inquiry as to the amount Mance°'^
of current taken to warm up the heater, I may say I have tested these
lamps for some thousands of hours at my private residence, and have
found that the heating current was rather more than that which the
lamp took after the heater was cut out of circuit. With regard to
suitability for alternating currents, my house is connected to the mains
of the Brompton and Kensington Company, which supplies alternating
current at loo volts, the pressure being extremely regular. I daresay
I have tried at least 20 or 30 of these lamps ; I have found their life
varied from 150 up to 800 hours. One of the causes of failure, as
already stated by Mr. Hammond, was that the lead up to the glower
failed just at the point of contact ; and I made the suggestion that the
contact should be arranged in the form of a ring, so that if the lower
portion of the ring gave way there would be still remaining the upper
portion of it, and the life of the lamp would be thereby prolonged. I
noted the current which all these lamps took very carefully, and I think
the statements which have been made by the inventor and those
interested in the exploitation of the Nernst lamp have been fully borne
out. As chairman of a company which supplies electric current, you
might perhaps think I am afraid of the effect that the lamp might have
on our revenue. But I myself welcome anything which will cheapen
and popularise the use of the electric light. There is no doubt that
the lamp takes one half the current of the present lamps, but 1 think
that long before the conservative British public have taken to the use
of the Nernst lamp they will have been educated up to requiring twice
the amount of light.

There is one rather important point which perhaps the author might
assure us about, and that is, how the lamp stands transport ? I made
some experiments myself with the replacement pieces in the earlier
days, when the lamp was nothing like so perfect as it is now. The
results of these experiments were not altogether satisfactory. This is a
most important point, as the lamps have to be despatched to the
furthest corners of the world.

Mr. Drake : I would like to answer Professor Ayrton's question.
The bottom curve was taken with lamps which started with about 2
watts per candle, instead of 17. Everybody tried to make the Nernst
lamp do more than it could do ; and we made experiments to see
if it would not be better in the end if we started at 2 watts, rather
than 17 which gave such a rapid drop in candle-power. We certainly
got a better result than is obtained from the lamps which are now
being put on the market.

The President : We have had this evening a very interesting
discussion. We have had Mr. Stottner, who represents the German
manufacturers of this new industry ; and then we have had Mr. Drake,
who not only represents the English Company, but is really more than
an ordinary Director, for he has done an immense amount of the actual
detail work himself with the Nernst Company. And we have had
Mr. Solomon, who, with Mr. Sheppard, has also done a great deal of

Vol. 32. 86

Mr. Drake.

The
President.

636 STOTTNER: THE NERNST LAMP. [Feb. 26th,

PrKidcnt Original work. I wish we could have had something from Mr. Sheppard
too. We have not heard anjrthing from the Ganz people on the
subject, and we have not a representative here from the Westinghouse
Company to tell us what is going on abroad. Before calling on
Mr. Stottner, I would like to say, partly in reply to Professor Ayrton,
that the manufacture of these filaments is exceedingly difficult, not
only as a matter of ordinary manufacture, but as a matter of very
intricate chemistry. One reason why the English Company, though
they did not make many filaments and lamps, got, in some cases,
particularly good results, was the enormous care they took over the
chemical preparation. Any one who is familiar with the chemistry of
the rare earths knows it is exceedingly difficult to purify many of them.
Some of them can only be purified by continual re-crystallising. And
in any case the purification of zirconia, which is one of the chief
components, is very difficult. As to the other part of the filament, it
is really a group of earths. You can buy "yttria" from a manufacturing
chemist, but you can never guarantee that any two bottles contain the
same substance. They are mixtures of the same group of oxides, and
it is very difficult to know exactly what you are getting. First, there
is the mechanical question, and then there is the chemical question.
It is apparently, exceedingly important to get the material out of which
the filament is made, in a given physical condition, especially to get it
sufficiently fine. A slight difference in this way made a great difference
in the life and the change of resistance of the filaments.

As to why a lamp should go down in life when, apparently, it is
controlled by a resistance which will practically keep the watts in it
constant, or nearly constant, that raises a very interesting question.
I do not want to contradict Mr. Campbell Swinton, but I think the
argument used by him ought to have the negative sign put before it,
because the conditions in the case of incandescent gas are exactly the
opposite of what they are here. In the case of the incandescent gas
lamp, if you increase the emissivity of the mantle you lower its
temperature and eventually its candle-power. But the mantle gets
more energy and gives more out, because it gains more from the gas,
and the whole question is different. What I think probably happens
in the case of the Nernst lamp is, that when the glower lamp gets a
little old the platinum from the contacts gets into the body and you
notice a slight graying of the filament, and this means an increased
emissivity and light-radiating power at a given temperature. And if
you keep the watts constants it radiates energy at a lower temperature
and probably gives loss light. Mr. Swinton's experiments in bombard-
ing thoria are not in the least conclusive, either as regards the Nernst
lamp or with respect to incandescent lamps for gas. When you are
bombarding you cannot tell whether the surfaces are at the same
temperature, though they may look so. If you take the trouble you can
find on purifying zirconia that eventually you can get a material which
you can make into mantles for gas lamps to give almost no light, but
they will give plenty as Nernst lamps, and they will give plenty of light
when they are bombarded. But that is a different thing, because when
you are bombarding you have not necessarily got them at the same
temperature.

903.]

THE NERNST LAMP : DISCUSSION.

537

Earl Russell {communicated) : Not being able to get into the room EariRosseiL
to take part in the discussion, I am compelled to send some observa-
tions in writing. The Nemst lamp is a very fascinating invention, and
the account by Mr. Stottner is very interesting, as I do not doubt the
exhibits were if I had only been able to see them. The lamp is
economical, and the light given by it is of a very pleasing quality.
But I am afraid a great deal has yet to be done in making the burner
run for a sufficient time. I have two Pattern A 1902 Nernst lamps, and
my experience with them has been unfortunate. The lamps are
105-volt, and they are run from accumulators only in which the usual
pressure is loi to 102 and never exceeds 104, so that they are not over-
run. Nevertheless, I find that instead of a life of, say, 300 hours, as
stated in the catalogue, the average life has been something like 20 hours.
The longest that any burner has run is about 3 months during the
lighter part of the year, representing perhaps 180 hours. On the other
hand I have had two burners going the next day after being put in :
two which refused to Hght at all, and three or four which had gone in
periods var)ring fron 9 hours to 40 hours. It is only fair to say that
so far the Electrical Company have been most generous in replacing
these early failures without charge, but of course one cannot say how
long that will go on. They practically always break at the same place,
that is the spiral part near the bottom. Another objection to their
commercial use at present is the limited range of candle-power, e.g.^
you cannot get more than a 60-candle lamp on a loo-volt circuit.
Although the replacement is easy, still it involves time and annoyance
(particularly if it has to be done in the dark) and the fetching of a pair
of steps, besides the cost of 2s. 6d. a burner. Until, therefore, a longer
average life can be given to the burners, I fear the lamp can hardly be
regarded as a success for use in private houses.

Mr. A. Wilson {communicated) : I am disappointed to find in the Mr. Wiiwn.
paper no statement as to the average life of the burners and resistances
of the Nernst lamps as at present placed on the market, and should be
glad if the author would give some information on that point. The
Company who have introduced these lamps have stated in one of their
pamphlets that the life of the burner averages 400 hours, but experience
with a considerable number of lamps leads me to believe that 200 hours
is a long life, and even that can only be attained by running the lamps
coosiderably below the total volts for which the combined burner and
resistance are marked. For example, in a factory in which over 100
Umps are used, with 220-volt burners and 20-volt resistances and with
never more than about 240 volts at the lamp terminals, the engineer in
charge stated that the average life of the lamps was about 40 hours.
By using i a 255-volt combination, i.e., 235- volt burner and 20-volt
resistance, and consequently under-running the lamp by 15 volts, the
life has been raised to about 200 hours, or about half of what it is
supposed to be, with, of course, a corresponding reduction in the
efficiency of the lamp.

The lamps undoubtedly give good light and are of high efficiency,
but the unreliability of the burners and the amount of attention
required in niaking replacements seems more than to balance any

538

STOTTNER : THE NERNST LAMP.

[Feb. 26th

economy which they are supposed to effect. I am quite unable to
reconcile the statements which have been published as to the life of
the lamps with my own experiences and those of many others under
ordinary working conditions, and take this opportunity of asking for a
statement on the matter from one who is apparently intimately
associated with the manufacture of the lamp.

Mr. J. Stottner, in reply, said : With regard to the remark made
by Mr. Drake about two filaments in one lamp, the construction is
shown in Fig. F.

I — vVW

Fig. F.

We put two filaments, which are connected in parallel, inside the
heater, the current passing through one automatic cut-out to the other
pole. One or other of the two filaments will be heated first — it is
immaterial which — and as soon as one is incandescent the heat
radiating from it will start the other filament and make it also a con-
ductor, so that there are two filaments and one conductor. Another
advantage of this arrangement is that if one filament breaks, or for
some reason goes off, the other is always intact and will act as if
nothing had happened.

The burners with horizontal filaments are a further novelty, they
are shown in Figs. G, H, K, and L.

The filament is in front of the heater, so that all the light radiates
directly downwards ; they can be arranged in any number. In these
lighting bodies the filaments can be taken out and easily exchanged,
the complete burners being fixed in the body of the lamp as in the
present design. The filaments are exceedingly simple and provided
with flexible conductors, which carry a small plug on each end for
connecting up. One hundred filaments can be got into a match-box.

Mr. Hammond, I am very glad to say, got about the same results as
the Physikalische Technische Reichsanstalt, which worked out the
average life of a lamp at about 450 hours, while Mr. Hammond got
305 hours. Had he had such clever experts to handle the lamps at

1903.]

THE NERNST LAMP : DISCUSSION.

539

Hackney as they have at the Physikalische Technische Reichsanstalt, ^r- ^^^
the results would doubtless have been still better. The reason why
the flexible at Hackney and many other places has failed is a very
simple one.

}

Fig. G.

o~^

Fig. H.

Fig. K.

The heater-coil, Fig. M, expands somewhat as soon as it is up to
temperature, and if the flexible wire a, which conducts the current to
the filament, is bent and touches the heater, it either burns through at 6,
should there be a bright spot in the heater spiral, or it burns the heater
wire through, as the resistance from 6 to c is very small. There would,

///M\\ /''\\^

/ / / n \ \ / /
i \ ^
• 1 * • . \ ^

Fig. L.

Fig. M.

however, be no difficulty in taking such a slight precaution as to
examine the filament after insertion. If the lamp does not light up, the
automatic cut-out does not act properly. The filaments and heaters
must be examined before they are put in, and if the heater does not
cease glowing as soon as the filament is incandescent, the contact-
spring of the automatic cut-out sticks and the inside of the lamp must
be examined.

540

STOTTNER : THE NERNST LAMP. [Feb. 26th,

Mr.
StStlncr.

The
President.

As mentioned by Mr. Swinburne in reply to Professor Ayrton, the
efficiency-curve of the lamps which Mr. Drake showed is very high.
We have not found such very high efficiency in ours. The light
certainly does go down after a lamp has been in use for a considerable
time, and the filament takes longer to heat up than it does when it
is new. The efficiency drops considerably because of the blackening
of the heater-coil and further on account of the crystallisation in the
filament, as is shown by a filament on the table before me, which has
burned i,6oo hours. As to the variation of voltage, 5 per cent, does
not make any material difference to the life of a lamp, but it is prefer-
able for it to go down than up. There was one station mentioned,
however, where the variation is a good deal higher than 5 per cent.
There may be a 20 per cent, variation. If the voltage rises too high,
the result is that the bolstering resistance burns through. It acts
as a kind of safety-fuse to the lamp if everything else is properly
arranged.

As touching the question whether alternating- or direct-current
lamps are the better ; — theoretically, alternating-current lamps should
be better but practically we find that direct-current lamps give greater
satisfaction. Whether this is because at the works the demand for
alternating-current in proportion to that for direct-current lamps is
about I : 500, and less experience has been gained, or whether there is
some other ground for this, I cannot say. The breaking of filament is
generally due to mechanical causes. Either they get knocked about, or
they break through vibration or through some other part of the lamp
not acting, as already mentioned. The electrolytic effect on the fila-
ment will in every case be exactly the same. There is no reason why
one filament should burn out more quickly through electrolysis than
another.

One speaker mentioned the packing and transport, which is a very
serious question, under which we have to suffer greatly. As a test of
average breakage we took two packages and tumbled them down four
Eights of stairs. On examination we found in one case two burners
broken out of 200 and in the other case five broken out of 400, which I
do not think is a very great percentage. With the new packing it will
be less still. The old packing was much less suitable for rough
handling in transit. I once caught one of our boys tossing three of the
old-style round boxes with burners like a juggler, which at once ex-
plained to me why some of the filaments break ; and other people may
have similarly playful boys in their employ.

The President : I will now ask the meeting to pass a very cordial
vote of thanks to Mr. Stottner ; and I have his authority to mention
that he hopes to present to the Institution museum, samples showing
the early history of this lamp.

The vote was carried by acclamation.

The President announced that the scrutineers reported the
following candidates to have been duly elected, viz. : —

1908.]

ELECTIONS.

641

Member,
WUson Hartnell.

Associate Members,

Frank Bradford.
Ashton Bremner.
Henry Coulson-Crawford.
James Cuninghame.

Albert William Davies.
Raymond G. Mercer.
Andrew Home Morton.
Frank J. Robins.

Associates.

Augustus George Ashton.

Malcom Rayner McClurc.

Students.

Arthur McL. Atkinson.
Herbert Frederick H. Blcase.
John Henry Clarke.
Ernest Francis Cutforth.
James Floyer Dale.
Walter Hugh St. A. Davies.
Oswald J. Davis.
Harold W. Fulcher.
Henry J. Golding.
George Goodwin.
Ernest James Harper.
Laurence E. C. Harrison.
Herbert H. Harter.
David Cecil Henderson.
Frederick Richard Hobley.
A. T. S. Hore.
James G. H organ.
E. Laubach.
Horace Hamilton Leage.

George Stewaf t

William E Cato Liebert.
Wyndham d'Arcy Madden.
Arthur Cecil Morrison.
Ernest William Moss.
Llewellyn Digby Odium.
Hugh Prideaux.
Hubert G. Ross.
Henry Eustace Sayer.
Herbert John Seale.
John Franklin Shipley.
Chas. Francis Simpson.
Benjamin Spalding Smith.
Joseph James K. Sparrow.
Wm. T. Tallent-Bateman.
David Alan Trickett.
Eric Charles B. Walton.
Eric Gordon Waters.
Thomas Douglas W. Weston.
Arthur Penry Williams.
Wilson.

642 HOLMES: ADDRESS AS CHAIRMAN [Newcastle,

NEWCASTLE LOCAL SECTION.

INAUGURAL ADDRESS OF THE CHAIRMAN.
By Mr. J. H. Holmes, Member.

(ABSTRACT,)
[Address delivered Ncn'cmber 17, 1902.)

In addressing you at this, the third inaugural meeting of the
Newcastle Local Section of the Institution of Electrical Engineers,
I wish, in the first place, to thank you for the honour you have con-
ferred upon me by electing me to the position of your Chairman for
the ensuing session.

I have no doubt that with your cordial support and assistance I
shall find the duties appertaining to the office as agreeable as they are
honourable, and that our united efforts will enable us to uphold the
status of the Institution and make the session a success. In the
remarks which I have the privilege of addressing to you by way of
opening our proceedings, I propose to glance at the influence exercised
by the great activity and rapid development of electrical engineering
upon other branches of the engineering profession.

We all have the honour of belonging to the noble profession of the
engineer to which modern civilisation owes so much. For, whether
it is within the sphere of the domestic circle or without, in the
strenuous life that daily confronts us, there is scarcely a comfort or a
convenience that exists to the realisation of which the engineer has not
largely contributed. Engineering has been defined as the art of
directing the great sources of power in nature to the use and con-
venience of man, and therefore the engineer is interested in every
investigation and discovery in the whole realm of science — his occupa-
tion is the most catholic of all. No sooner does an abstract theory
become a demonstration than the engineer seizes it and applies it to
man's uses.

Some discoveries burst upon us with a blaze of light attracting
universal attention, and inventions follow with lightning speed, whilst
others develop so slowly as almost to pass unnoticed.

The branch of engineering with which we are so intimately
concerned, whilst most far-reaching in its consequences, is, when
measured by the mere lapse of time, but of recent growth, yet,
measured by its phenomenal progress, is quite ancient, and already
embraces so many distinct branches that it has become practically
impossible for one man to keep pace with the developments almost
daily occurring in its many sub-sections.

Young, however, as the profession of electrical engineering is,
I think wc may justly claim for it, that it has exerted a greater

1902.] OF NEWCASTLE LOCAL SECTION. 548

influence upon engineering as a whole than any other individual
branch, and we may profitably spend our time by glancing at a few
instances of the kind.

A dynamo, as we all know, is the agent by which mechanical power
is converted into electrical energy. The prime mover is usually a
steam engine which has a reciprocating motion, which, by the aid of a
crank, is converted into a turning movement. By the very nature of
things an unequal torque is the consequence, leading to a pulsatory
motion of the dynamo. There is no more exacting duty for a steam
engine than that of driving a dynamo for any purpose, but particularly
for lighting, where a pulsation or rising and falling in the intensity is
most distressing. Hence in the early days to drive a dynamo by
means of the existing engines was like driving a square peg into a round
hole, and the steam engineers were immediately confronted with the
problem of how to get a uniform angular velocity which was
extraordinarily important in running alternators in parallel. It is
interesting to recall the various methods employed to meet the case.
How eagerly the problem was struggled with more or less satisfactorily
in many different ways.

The early dynamos were run at high speeds obtained by belt-
driving through gearings or countershafts, which was soon recognised
as wasteful of power, and the difficulty was met by increasing the
engine speeds, which drove out the large long-stroke slow-moving
heavy engines in favour of small short-stroke quick-moving light
engines driving by belting direct from the flywheel. But this was not
enough, because dynamos had a variable load, hence the makers of
small engines were compelled to introduce improved governors and
heavy flywheels. These took the form of high-speed throttle
governors spring-controlled, only to be superseded by automatic
expansion governors, which, in their turn, were replaced by shaft
governors revolved at engine speed.

Heavy flywheels on engines used specially for driving dynamos for
traction purposes, where the alterations in load are both frequent and
rapid, did very good service, securing a relatively constant angular
velocity for that class of work.

To sum up, the dynamo with its high speeds forced on the balancing
and governing of steam engines to a point that was never dreamed of
as necessary before.

Another problem was that of lubrication. Continuity of run over
long periods called attention to the need for unfailing lubrication, the
oil cup of old being superseded by centrifugal oilers, and a few hours'
run being lengthened out into fifteen or more, and finally to continuous
running, as in the marine engine. This led to the employment of
pipes and wipers fed from oil-cups, and later from a central oil-box
with sight feeds. Then to independent oil-pipes to each bearing
surface, conveying oil at a pressure of 20 lbs. to the square inch, main-
tained by a force pump. And perhaps in the most advanced way in
enclosed engines such as the Willans or Chandler, where the moving
p>arts practically splashed about in a bath of oil and water, effectively
lubricating all the bearing surfaces. However, all experience having

644 HOLMES: ADDRESS AS CHAIRMAN [NewcasUe,

shown that the balancing of parts, the perfection of lubrication
continuity of run, small occupation of valuable space, and absence of
great watchfulness as essentials in electrical machinery in up-to-date
power-houses, it is brought forcibly home to every one that in Parsons'
turbo-generator, which has been gradually developing of recent years,
these qualities are embodied, combined with a reasonable steam con-
sumption, to so great a degree as to bring the Hon. C, A. Parsons'
invention into the foremost rank of all prime movers, and I am sure I
voice the feeling of all in being proud to note that our esteemed
member has been awarded the Rumford Medal by the Royal Society
in recognition of his important work. Useful as this steam turbine is
in electrical work, its application to marine propulsion bids fair to rank
as a still greater achievement.

Measurement of Power, — The simplicity and exactitude of electrical
measurements has exerted a very great influence upon questions
relating to the efi&ciency of steam engines, both as regards steam
consumption and the internal losses in the engine itself.

Water Cooling. — How to cool water for condensing purposes, that
great aid to the economical application of steam power, is one of the
electrical engineer's difficulties in cities where cooling ponds and
running streams are absent. This has been met by the introduction of
cooling towers, economical at their load, and certainly a fairly successful
mode of meeting what is a difficulty in most cases.

Gas Engines, — Strange as it may seem, it is nevertheless true that
it was many years before the electrical engineers could convince the
gas-engine makers that the pulsation in lighting from gas-driven
dynamos was not inherent to the dynamos.

In the Otto cycle method of working, where the compression of the
mixed gases before ignition is a great improvement, in the single-
cylinder engine, as only every fourth stroke is effective (the other three
absorbing energy stored in the flywheel), a variable angular velocity
results. This is met by high speeds and very heavy flywheels placed
on the engine, which is the right place, and not on the dynamo spindle,
which is the wrong place.

As the heating of gas-engine cylinders is proportional to the work
done, over-heating had to be met by water jacketing, involving in-
creased tank capacity and more room for the extra cylinders, a
condition unknown in intermittent work for which the gas engine was
in the main designed in the first instance.

Quite recently, large power producer-gas engines, such as the
" Diesel," consuming crude petroleum finely sprayed into the combus-
tion chamber, have been introduced highly suitable for driving
dynamos with economy.

Transmission of Power, — In the transmission of mechanical power
I claim that the electrical engineer has exercised extraordinary
influence.

Belting, — ^The increase of transmitted power through using higher
speeds in running shafting and belting was but dimly recognised until
forcibly brought under notice by dynamo working.

Inequalities in laced belting joints caused jerks in running over

1902.] OK NEWCASTLE LOCAL SECTION 646

d3mamo pulleys, and 'led to endless §ewn joints for smoothness in
running and dynamo slide rails for taking up the slack caused by
stretching.

Then to obtain greater equality and avoid slip the leather link belt
was devised, each link becoming a joint. The extra weight of this
form of belt was of advantage when used with the top side slack, as it
should be, as its sag embracing a larger arc of contact on the pullies
reduced slip, even when the shafts were comparatively close together.
But a laminated belting composed of long strips of leather placed on
edge side by side until the required width is obtained, then closely
sewn through, best fulfils the requirements for the transmission
of power.

Small Steam Pipes. — The great economy in the electric transmission
of power by means of wire conductors has opened the eyes of the
owners of works to their losses in that most wasteful method of power
transmission by distributing steam from a central point by means of
steam pipes, either underground or overhead, to small engines at a
distance. Enterprising men, especially shipbuilders, have realised
large economies, first by diminishing labour by concentrating their
generating plant in one shop, and, secondly, by replacing their
notoriously inefficient scattered small steam engines by electric motors
deriving their energy from compound or ttiple condensing engines.
The electric motor only draws energy as the work needs it, the waste
in distribution by electric conductors is trifling, the daily upkeep is
small, and the arrangements are simple in control. These advantages
presage the early supersessions of steam-power distribution, and also of
hydraulic-power distribution. Lifts or elevators are now mostly
electrically worked, and cranes and capstans for docks and warehouses
are rapidly following suit

In overhead travelling cranes the usefulness of three motors versus
one motor is moving in favour of three motors, because of the peculiar
feature of electric driving previously mentioned — the absence of loss
of energy excepting during actual running of the motor which exactly
fits intermittent work.

The slow speed of the chain drum has called for improvements in
gearing, leading to the use of raw-hide gearing, double or triple thread-
worm gearing running in an oil bath, of friction gear, and in some cases
the epicycle train.

The propulsion of vehicles is of immense importance, and the
electric influence is daily more marked. Indeed, it is evident that we
are on the threshold of huge developments in this direction.

Even the large railway companies have been stirred, and it looks as
if Newcastle, the birthplace of the locomotive, will also be the pioneer
in the use of electric haulage. If not, it is safe to predict that the
electric tramways service, which is now developing so marvellously,
will still further diminish their receipts.

Electric tramways must work a complete revolution in social life,
inasmuch as their cheap rapid and pleasant transit brings town and
country into closer touch, spreading the population over a wider area,
discrediting jerry-built flats in favour of garden cottages.

546 HOLMES: ADDRESS AS CHAIRMAN [Newcastle,

For all automobile work electricity is by far the cleanest and
most agreeable agent, and much development may be looked for in
this direction.

Socially, the influence of the electric light has been most marked ;
it has lent brilliancy to internal lighting by the use of the arc, and for
decorative purposes the glow-lamp is supreme, whether it be for
advertisement or for social gatherings. It has stimulated the use of
light ; that which used to be considered sufficient is now considered
inadequate, what would formerly poison the atmosphere and dirty ali
decoration now simply makes home cheerful, and vitiation of the air
is overcome whether in the theatre or the home.

The reaction upon the gas industry has been immense ; the gas man's
monopoly has gone, and with it his lethargy, leading to the regenerative
gas-burners of Siemens and Wenham, and the Welsbach light ; and,
latterly, the Kitson modification of the Welsbach, with its low cost and
rivalry of the electric light ? Similarly in fittings, the artistic designs in
graceful lines to please architects have stimulated similar improvements
in gas-fittings. And as to ocean steamers, what would they be without
the electric light ? and shortly what will they be without electric
winches, windlasses, fans, which are fast superseding small engines
and leaky steam-pipes ?

Then, again, what an influence electric search and other lights have
had on the mercantile marine, doubling the capacity of the Suez
Canal without cost, where 90 per cent, of the vessels that pass through
save fourteen hours per trip by its agency.

The coal miner now signals, blasts, and lights electrically ; also
pumps, hauls, drills and cuts his coal electrically.

The gold miner converts water power into electric power, and by
its agency crushes ores and uses it for all mechanical purposes.

Edison separates iron ores formerly useless for the smelter, and
electricity plays a prominent part in reducing and refining, whilst the
electric furnace also produces aluminium, sodium, carborundum, and
calcium carbide now, and will, probably, other substances shortly.

Of course of the oldest of the electrical industries, telegraphy, and its
development telephony, much can be said ; what was a luxury is now
a necessity almost as much as the sun itself, for by its commercial
agency the business of equalising the products of the world for feeding
its inhabitants is consummated.

As for wireless telegraphy, with which Marconi's name is linked for
ever, it should be as useful to fleets at sea as the ordinary telegraph is
to railways on land, and what more may be in store only time will
reveal.

Again in the case of the body, for nervous troubles, for baths, for
cauterising, for ameliorating skin diseases and looking into our
interiors with Rontgen rays, how can we do without it ?

I trust this rapid glance at some of the instances of the influence of
electrical on other branches of engineering has served to remind us
that we belong to a profession which, though young, has played an
important part in the march of progress recently, and promises a more
rapid advance than ever now. Electricity now permeates every

1902.] OF NEWCASTLE LOCAL SECTION. 547

branch of business ; it is no longer an abstruse science, and every one
who takes an intelligent interest in what goes on around him must
acquire some knowledge of its behaviour ahcl uses.

By creating new needs electricity has stimulated the other branches
of the profession in a very marked manner, quite beyond the stimulus
of competition in their own lines.

It would be too big a subject to enter upon the question as to how
far our present standard of civilisation would be possible if electricity
were absent from our calculations, and I must leave this for each of
us to think out for himself.

If I have succeeded in impressing upon any one of my hearers
a higher opinion of the usefulness and importance of the work upon
which he is engaged, and of the nobility of his profession, I shall be
amply repaid for what, after all, arc, I fear, but feeble efforts to do
justice to a theme which is worthy of a much abler pen than mine.

648 LEA: ADDRESS AS CHAIRMAN [Birmingham,

BIRMINGHAM LOCAL SECTION.

INAUGURAL ADDRESS OF THE CHAIRMAN,
By Mr. Henry Lea, Member.

(ABSTRACT,)
(Address delivered December lothy igo2,)

From time to time, particularly since the advent of electricity as a
producer of light and a distributor of motive power, we English
engineers have been charged with being laggards. I am not one of
those who believe that we are in a bad case, and I propose to try this
evening to ascertain whether the state of one industry at all events,
namely the electrical industry, is calculated to afford encouragement
to ourselves and the country generally, or whether the gloomy views so
often expressed are in any sense justified. My aim this evening will be
to obtain a general idea whether the Electrical Industry is growing, or
standing still, or going backwards. The period selected for scrutiny
comprises the years 1898 — 1901, four years being quite enough, in my
judgment, to show which way the stream is flowing.

The first point that I shall bring before you relates to the growth of
the manufacture of steam engines for driving dynamos. Nineteen
large firms were good enough to respond freely to my inquiries. The
results which I shall place before you are the collective totals of the
returns of all the firms who have been good enough to give them in
each case, and whilst they must not be taken as being in any sense the
totals of this country's production, they may, I think, be fairly regarded
as representative of the industry generally.

Steam Engines.

Confining myself then at present to steam engines made by nineteen
firms only, I find the following results : —

1. Numbers of Steam Engines turned out for the sole purpose of driving
Dynamos : —

1898.— 967.

1899. — 1,649, an increase of 71 per cent, over 1898.
1900. — 1,655, an increase of, say, i per cent, over 1899.
1901. — 1,836, an increase of 11 per cent, over 1900.
1901 shows an increase of 90 per cent, over 1898.

2. B.H,P, of the same Engines in nearest round numbers : —

1898.-86,000.

1899. — 168,000, an increase of 96 per cent, over 1898.
1900. — 210,000, an increase of 25 per cent, over 1899.
1901. — 295,000, an increase of 41 per cent, over 1900.
1901 shows an increase of 243 per cent, over 1898.

1902.] OF BIRMINGHAM LOCAL SECTION. 649

The extremely rapid growth in horse-power as compared with the
much slower growth in numbers of engines indicates that the sizes of
the engines are increasing. Thus,

3. A verage Horse-Power per Engine : —

1898.— 89 H.P. each.

1899. — 102 „ „ an increase of 15 per cent, over 1898.

1900. — 127 „ „ an increase of 26 per cent, over 1899.

1901. — 161 „ „ an increase of 24 per cent, over 1900.

1901 shows an increase of 81 per cent, over 1898.

I think you will agree that, at all events as regards steam engines for
producing electricity, there has been nothing during the last four years
to dishearten the people of this country

Continuous-current Machinery.

Now let us turn to the output of dynamos and motors, taking first
continuous-current machines. In this connection the number of finps
furnishing returns is 17 only.

1. Numbers of Coniinuous-currcni Machines, including both Dynamos
and Motors : —

1898.-2,540.

1899. — 4,736, an increase of 86 per cent, over 1898.
1900. — 5,095, an increase of 7 per cent, over 1899.
1901. — 6,799, ^^ increase of 33 per cent, .over 1900.
1901 shows an increase of 168 per cent, over 1898.

2. Power of Continuous-current Dynamos and Motors in Kilowatts
(nearest round numbers) : —

1898.— 39,300 K.W.

1899. — 65,200 K.W., an increase of 63 per cent, over 1898.

1900. — 83,600 K.W., an increase of 28 per cent, over 1899.

1 901. — 107,400 K.W., an increase of 40 per cent, over 1900.

1901 shows an increase of 174 per cent, over 1898.

A fact that has become evident during the last four years has been
the growth in the use of multipolar machines for continuous currents.
The matter is not very well understood, and manufacturers have been
largely in the hands of consulting engineers. A multipolar machine
can be constructed at low cost to give very high efficiency as regards
CR losses, but it is a much more difficult matter to get over iron losses.
The last four years have seen a great increase of knowledge on this
subject. The correct construction and subdivision of the magnet
cores, the correct proportioning and the number and size of slots in the
slotted armature cores, have during the past four years received increas-
ing attention, so that if we now compare the most economical multi-
polar machine with the most economical bipolar smoothed core arma-
ture of ten years ago, we find the former has at length equalled the

660 LEA: ADDRESS AS CHAIRMAN [Birmingham,

economical efficiency of the latter ; whereas for a long time following
the first introduction of multipolar machines, although they were always
a better mechanical job they were, on account of their heavier iron
losses, behind the older machines in efficiency. Consumers as a rule
did not appear to understand this, and demanded the same high effi-
ciency from the modern multipolar that they were in the habit of
obtaining from the old smooth-cored bipolar, but, for the foregoing
reasons, manufacturers failed for a long time to turn out multipole
dynamos or motors within the specified limits of efficiency.

Ten years ago the iron and core losses of the bipolar machines
made by several leading firms were under i per cent, but the C'R
losses were only kept down to 3 per cent, by the profuse and costly
use of copper in the armatures and fields. In these days the same
total efficiency is obtained, but the distribution of losses is reversed ;
the C'R losses can be kept down to i per cent., while the core losses
are with difficulty reduced to 3 per cent.

Alternating-current Machinery.

The makers of this class of machinery are comparatively few in
number, and as regards three-phase work have not long been engaged
in the production of such machines. The most that the returns show
is that this branch of British industry is receiving some attention,
though real activity of growth has yet to come. Grouping together
single-phase, two-phase, and three-phase machines, the following are
the results of the returns (from five firms) of generators and motors
combiried ; —

1898. — 35 machines, output 9,322 K.W.

1899.— 37 „ „ 8,974 „

1900.— 39 „ „ 8,209 »

1901.— 77 „ „ 8,165 „

The increase in the output of polyphase machinery abroad is due
in the main to the fact that local conditions gave rise to a demand for
it, whereas no demand for this class of machinery existed at home.
Moreover, the position of the patents is very ill-defined, and few firms
here have thought it worth while to lay themselves open to an infringe-
ment action simply to be able to fill a limited number of orders for
power distribution and mining work. No doubt this position will
soon alter itself, though as regards the use of polyphase machinery in
ordinary factory work the want of flexibility of speed control militates
against its application in this direction, where minute speed regulation
appears to be of increasing importance.

Standardisation.

Although there certainly has been a very substantial increase in the
output of electrical plant during the four years which I have selected
for comparison, yet it is probable that the increase would have been
still greater if, a few years ago, the engineering interests concerned
could have arranged for a certain amount of standardisation. Consider

1902.] OK BIRMINGHAM LOCAL SECTION. 551

two firms of equal size and equal manufacturing capacity, one of which,
" A," manufactures 50 patterns, and the other, " B," manufactures
100 patterns, both following the modern principle of manufacturing
compK>nents and afterwards making them up as the orders come
in. With an equal stock of tools for turning out these components,
and with equal money value of components kept in stock, the firm *' A "
that works on only 50 patterns will be able to execute an order for any
one of these patterns in half the time that the firm " B " will require
that has 100 patterns. Then, as the time for executing the order is
shortened, so may, for equal dividends paid, the price per article be
reduced. The firm "A" therefore manufacturing in less time than
*' B," turns over its capital in pro rata less time than " B," and con-
sequently may be satisfied with a less percentage of profit, and yet pay
an equal dividend. Thus quick delivery and low prices go together
and help one another to enable the firm "A" to keep its order sheets full.

I imagine that no manufacturing firm exists that would not, if it
could, standardise everything it makes, and work to jigs and templates
throughout, but in a new industry experiencing a rapid development
it is not possible to standardise at an early stage. The process of the
survival of the fittest is going on in its usual relentless fashion, and a
too early endeavour to standardise would only mean a heavy loss in the
abandonment of superseded special tools, or in the remodelling of them
to suit the inevitable alteration in pattern. Between these two sets of
imperious conditions, on the one hand the urgent necessity for
standardising, and on the other hand the danger of doing so too soon,
stands the manufacturer, and happy is he whose customers realise the
desirability of establishing standards at the earliest practicable point in
the history of the development, and so lend a hand in facilitating the
manufacture of interchangeable machines.

The Institution of Civil Engineers, with the Institution of Mechanical
Engineers, the Institution of Naval Architects, the Iron and Steel
Institute, and our own Institution, have now a joint Standardising Com-
mittee in full swing, and there is hope that something may be done in
the matter, and that consulting engineers and manufacturers may find
themselves able to co-operate towards so desirable an end.

Power Schemes.

This subject is wide enough for a long special paper to itself. I
cannot do more than briefly refer to it. The scope for constructive
business is enormous. The scope for skill to make all the proposed
schemes pay well is equally great. I think it may be taken that it will,
generally speaking, be no part of the Companies* programmes to com-
pete with the electric light undertakings in their districts, but, on the
contrary, to assist the local authorities to obtain Provisional Orders,
and to supply them with power in bulk, which they may retail to the
inhabitants of their areas.

Traction Work.

Under this heading I include tramways and light railways, but not
railways other than light railways. The progress in this branch of the
Vol. 32. 87

662 LEA: ADDRESS AS CHAIRMAN [Birmingham,

industry has been marked, but not nearly so rapid as in the other
branches previously referred to. The great growth has yet to come,
and there are indications that it will be of vast proportions.

The number of firms who in this country make tramway motors is
very limited, but the industry is rapidly growing. From the returns
which I have received, the output for the year 1901-2 was nearly 40 per
cent, in excess of the output for the year 1900-1. Of the total number
of cars now running in England, upwards of 80 per cent, of them have
motors manufactured in England, and the importation of such machinery
is decreasing rapidly.

I will present to you the growth from two points of view, namely,
(i) the mileage and number of cars ; and (2) the amount of capital
invested.

I. Route Mileage and Number of Cars.

ROUTE MILEAGE.
1898.-365.

1899. — 478 = 31 per cent, increase over 1898.
1900.-576 = 20 „ „ 1899.

1901.-777 = 35 „ „ 1900.

1901 shows an increase of 112 per cent, on 1898,

NUMBER OF CARS.

1898.-2,117.

1899. — 2,654 = 22 per cent, increase over 1898.
1900.-3,033 = 14 „ „ 1899.

1901.-3,821 = 26 „ „ 1900.

1 90 1 shows an increase of 73 per cent, on 1898.

2. Capital Invested (nearest round numbers).

1898

Companies

9,800,000

1899

Companies

11,800,000

Municipalities ...

1,170,000

12,970,000

= 33 per cent, increase over 1898

1900

Companies

14,560,000

Municipalities ...

2,750,000

1*7 '5 in rtrtt\

*7>3**^»^^^^^

= 33 per cent, increase over 1899

I90I

Companies

19,750,000

Municipalities ...

10,520,000
30,270,000

= 75 per cent, increase over 1900.
1901 shows an advance of 210 per cent, increase over 1898.

It may be of interest here to remind you of two examples of tram-
way work carried out on novel lines. At Wolverhampton we have the
Lorain surface -contact system at work, so far successfully, though a
crucial test would be a severe winter with plenty of snow and salt-
Then in London we have an extensive conduit system about to get to
work.

1902.] OF BIRMINGHAM LOCAL SECTION. 663

Electrificatiox of Main Lines of Railways.

On the North Eastern Railway a portion of the system is about to be
electrified upon a good working scale, and much practical information
will no doubt be derived from it later on. It may be regarded as the
first attempt in this country to displace existing locomotives. The
converted hues will be those running from Newcastle-on-Tyne to
Gosforth, with some smaller branches. The main object of the con-
version from steam to electricity is to compete with the electric trams,
so that the scheme will be laid out as much as possible to look
primarily after the passenger traffic.

The employment of electricity for the special purposes of under-
ground railways, or for a new overhead line as in Liverpool, can hardly
be looked upon in the same light as the N. E. R. experiment, which is
undoubtedly in the direction of displacing steam locomotives from the
ordinary main lines of railway in this country. It is, however, a far
cry from motor coaches of i6o H.P. each to trains requiring engines to
work them capable of developing up to i,ooo H.P., which power can be
exerted by some of our main-line engines. The steam locomotive may
be doomed, but I cannot help thinking that it will die hard, and I for
one shall be very sorry when they are no longer to be seen doing the
excellent work which they undoubtedly can do. When, however, this
country has been cleared of them, I shall probably not be here to see
the result.

A great deal has been said from time to time to the effect that by
means of electricity alone and a straight mono-rail track, speeds of loo
miles an hour become possible, and that one reason for this is that the
employment of reciprocating parts, as in an ordinary locomotive,
prohibits their use for those speeds. In my judgment there is
absolutely no foundation for this statement. The only reason why our
locomotive engineers have not hitherto enabled us to travel at, say, loo
miles an hour, is that they have never been asked to do so, and if asked,
have not had suitable roads with suitable curves and suitable gradients
for doing so. If it were decided to run at loo miles an hour, first of all
it would be necessary to lay a straight, or a very nearly straight track
built in the very best modern style. They would then probably elect
to draw trains of the same length as those proposed to be drawn on the
electrical system, namely, one or two long corridor coaches. At
323 r.p.m. a modern locomotive having driving-wheels 6 ft. 6 in.
diameter travels at the rate of 75 miles per hour, and this speed
is an everyday performance on our main lines. The presence of
reciprocating parts does not prohibit such speeds, nor do the engines
appear to sufifer therefrom. I have it from one of our most eminent
locomotive superintendents that the maximum limit might be fixed at
350 r.p.m. Taking, however, the above-named lesser and everyday
number of 323 r.p.m., the diameter of the driving-wheels for 100
miles an hour would have to be 8 ft. 8 in., or 11 inches only larger in
diameter than the 7 ft. 9 in. wheels, numbers of which are already to
be found on our main lines, and doing excellent work/ It would be
absurd to pretend that a locomotive engine with 8 ft. 8 in. driving-

664 LEA : ADDRESS AS CHAIRMAN [Birmingham,

wheels could be built to take one of our long trains of, say, 14 coaches
at anything like 100 miles an hour ; but if the train be reduced to the
length proposed for electrical propulsion, then a steam locomotive
could be built of sufficient power to deal with it, and if the reciproca-
tions of the engine were kept down to the present maximum number
per minute, there would be no more difficulty in relation to the recipro-
cation of the parts than there is now. The conclusion is that it is by
no means necessary to fly to electricity for speeds of 100 miles per
hour. The steam locomotive will easily give those speeds if they are
really wanted on tracks specially laid down for the purpose. The
smoothness and steadiness with which one travels at 75 miles an hour,
or even at the 86 miles an hour which have been attained on one of
our main lines, preclude entirely any apprehension that at a speed of
16 per cent, in excess of 86 miles an hour the smoothness and
steadiness would be in any degree inferior upon an ordinary first-class
double-rail track laid sufficiently straight for the purpose.

Railway Station General Purposes.

On the London & North Western Railway at Crewe extensive
alterations, involving amongst other things the enlargement of the
station and junctions, the addition of some 50 miles of sidings, and the
erection of a large transhipment goods warehouse, called for some well
considered scheme for lighting and working them. For power
purposes, instead of enlarging or reconstructing the hydraulic plant,
the latter has been abandoned, and electricity alone is used for all
purposes. The power-house has a capacity of about 1,000 H.P.

The growing utilisation of electricity for general railway purposes
cannot be better shown than by quoting the following instances on the
N.E. system : The operation of travelling jib cranes and of capstans at
Middlesbrough and West Hartlepool, the equipment of the York
carriage works with electric overhead travelling cranes and motor-
driven machinery, electric overhead conveyors for goods at York
goods warehouse and at Newcastle, electric overhead travelling cranes
at the Shildon wagon shops, together with motors for driving
punching, shearing, etc., machines ; contemplated experiments with
the electric lighting, of signals at Middlesbrough and Leeds ; at York
the ticket-printing machines are electrically driven, and at Newcastle
the ticket-destroying machine; the new locomotive shops at
Darlington are also being equipped with large electric overhead
travellers for lifting locomotives, etc., etc.

Railways Points and Signals.

I have included this subject because points and signals require a
considerable amount of power to work them with certainty under all
conditions, involving the use of electric motors for the purpose. The
examples are but few in number, and indeed I am unable to place
before you any particulars other than those which Mr. F. W. Webb, of
the L. & N. W. Railway, has been good enough to send me. Ten signal
cabins at Crewe are now worked or arc about to be worked by

1902,] OF BIRMINGHAM LOCAL SECTION. 566

electricity. In all they will contain i,ooo levers. One of them will
contain 350 levers, the largest signal cabin in fhe world. The whole
are interlocked much in the same way as on the old plan. The use of
them does not involve any fresh training of the signalmen. The
levers are, in fact, switch levers only, controlling motors or long pull
magnets or solenoids, as the case may be, and producing eventually
the same results exactly as the old levers produce. How the life of
these switches will be affected by the constant sparking remains to be
seen, though, if they are made with carbon tips, renewable contacts,
and have magnetic blow-outs, it is probable that they will wear well
and give but little trouble.

Gas Engines for Driving Dynamos.

I should like to have gone into this subject in considerable detail,
but time forbids me to do so. The matter has been recently dealt
with by Mr. Humphrey, of the Brunner Mond Company, in a very
comprehensive manner, and the present occasion is not at all a
suitable one for an attempt to vie with him. One aspect of the case,
however, I should like to lay before you. The gas-engine makers of
this country, who have turned out thousands of most excellent
engines, have for some years past had before them the object lesson
of the now almost universal adoption of the inverted vertical steam
engine for driving electric generators. The demand arose chiefly
from the fact that such engines occupy far less floor space than any
other, and that economy of floor space has become of essential im-
portance. Also that it is easy to construct on that system three-cylinder
engines with all the advantages of even turning moment which they
possess. The gas-engine makers must have realised that eventually
large gas engines would run steam engines very hard economically and
in other ways, and notwithstanding this they have allowed America to
take the lead in producing engines of this type. Any one who has had
to do with these engines cannot but appreciate the straightforward
simplicity of the three-cylinder arrangement, the ease with which they
are started, the excellent governing, and the extremely smooth way in
which they run. My firm has had the privilege of engineering a
gas-engine generating plant of, eventually, 1,200 H.P. at the
Birmingham Small Arms Company's factory, and, being unable to
obtain such engines in Great Britain, we were obliged to order them
from America. So far, they have given us every satisfaction, excepting
on the important point that they were not designed and built in our
own country, which I must admit is a truly saddening consideration.
There is nothing left for our own makers to do but to copy, unless it
be, while following the type lead, to produce something even better
than the American engines. Recognising as I do their undoubted
ability and skill, I most sincerely hope that we may be within measur-
able distance of. finding that they have accomplished such a highly
desirable result.

Measuring Instruments.

Ammeters and voltmeters are the principal measuring instruments

556 LEA: ADDRESS AS CHAIRMAN [Birmingham,

used in the Electrical Industry, and during late years considerable
differentiation in th^ types used for direct-current circuits and
alternating-current circuits has taken place. Formerly instruments
containing soft iron were largely used for both D.C. and A.C. systems.
Now it is customary to employ moving coil instruments in the former,
and hot wire or •* induction " instruments in the latter. Electrostatic
instruments are used in both systems, more especially in high-tension
and extra high-tension work. The adoption of moving coil voltmeters
on D.C. circuits has much to recommend it, for they are dead beat,
quick in action, free from hysteresis errors, and economical as regards
power expended in them. The same may be said of moving coil
ammeters for currents of moderate strength, but for very large currents
the power spent in ammeter shunts becomes a source of expense,
inconvenience, and inaccuracy. This arises from the fact that such
ammeters require the same P.D. to produce full deflexion whether they
are for large or small currents, and as this P.D. is usually about one-
twentieth of a volt, the loss in a shunt for 5,000 amperes amounts to a
third of a horse-power at full load. This disadvantage is minimised in
some cases by using part of a 'bus-bar or feeder as the ammeter shunt.
The fact that only comparatively thin wires need be led to the
indicating instrument is a great advantage.

For measurements in which high accuracy is necessary the ordinary
moving coil ammeter suffers from temperature errors, owing to possible
differences in temperatures and in temperature coefficient of the shunt
and instrument. Fortunately these errors may be greatly reduced by
the use of Campbell's bridge compensating arrangement described in
his patent of March, 190 1. It is satisfactory to learn that Messrs.
Elliott Bros, are introducing this compensation in their "Century"
testing sets. Moving coil voltmeters of ordinary ranges have little
temperature error, for they can be sufficiently ballasted by series
resistance of negligible temperature coefficient.

Hot-wire ammeters for very large currents are open to greater
objection, as regards expenditure of power, than moving coil instru-
ments, and in addition to this they are slow in taking up their steady
readings even when the current through them is quite constant. This
latter defect renders the instrument unsuitable for precise measure-
ments in circuits where the current fluctuates. One means of reducing
these defects is to use a series transformer with an unshunted instru-
ment in its secondary circuit.

On high-tension or extra high-tension systems hot-wire voltmeters
when direct-connected arc very wasteful, owing to a certain current
being necessary to cause the deflexion, but here again the consumption
of power can be lessened by using step-down transformers.

Electrostatic voltmeters need no step-down transformers or other
pressure changing devices, and are extremely economical in power.
They have, therefore, come into extensive use in high-pressure stations.
An important consideration in connection with alternating-current
instruments is their behaviour under different conditions of wave-form,
and in this respect hot-wire and " induction " instruments have decided
advantages over the soft-iron type. As " induction " instruments take

1902.] OF BIRMINGHAM LOCAL SECTION. 667

less power than hot-wire ones, and are usually more robust, they are
coming rapidly to the front.

The measurement of power in alternating-current circuits has
attracted considerable attention within recent years, and numerous
wattmeters have resulted. A large number of instruments has also
recently been invented to simplify and expedite the measurement of
permeability and hysteresis of iron and steel. The instruments of
Drysdale, Searle and Hoiden are perhaps the most novel of these
productions. It is to be hoped that these contrivances will induce
users of iron and steel for magnetic purposes to test consignments
themselves.

Within my four years period, one instrument has been brought out
which, to my mind, is the most interesting that has been devised
for many years, and is well worth our attention for a short time. I
refer to Mr. DuddelFs oscillograph. My admiration of it must be my
excuse for bringing it alone before you this evening. Through the
courtesy of Mr. Duddell I am able to show you the instrument in
operation, and I am very much indebted to Mr. Duddell for the loan of
the instrument, and to him and the sta£E of the Electrical Engineering
Department of this University for the trouble which they have taken in
setting up the instrument and all the accessories on this occasion.

At the end of the Chairman's address a demonstration was given,
showing the capabilities of the Duddell Oscillograph. The experi-
ments were conducted by Mr. Duddell himself.

658 EARLE: ADDRESS AS CHAIRMAN [Manchester,

MANCHESTER LOCAL SECTION.

INAUGURAL ADDRESS OF CHAIRMAN,
By Mr. H. A. Earle, Member.

{ABSTRACT.)

{Address delivered January 20, 1903.)

It is with pleasure that I avail myself of this opportunity to express
my thanks to you, who, as members of the Institution of Electrical
Engineers representing the Manchester Section, have paid me the
compliment of electing me your Chairman for the present session. It
is a compliment which I greatly appreciate. The growing importance
of the Manchester Section of the Institution is most opportune at a time
when the electrical industry is making rapid and important strides here.
As a centre for electrical works in this country, Manchester and district
is now the largest and most important. Moreover, Lancashire and the
neighbouring county of Yorkshire will, within a comparatively short
period, possess electrical generating stations which will be second to
none in the country as regards either size or importance. Besides the
large municipal supplies in Manchester, Liverpool, and other towns
the Lancashire and the Yorkshire Power Companies will shortly start
operations; and, notwithstanding the progress of the past, we may
confidently anticipate a development in the future which will surpass
anything we have witnessed.

With regard to progress in the past, those who have been
associated with Electrical Engineering during the last twenty years
have witnessed a development and application which the most sanguine
could hardly have anticipated. Within the period named the investiga-
tions, inventions, and developments which have chiefly contributed to
the advancement of the industry are : —

The production and commercial manufacture of the high-voltage

incandescent lamp.
The mathematical treatment of the fundamental principles of the

electric generator.
Tlie three-wire system.

The series-parallel control for traction work, and
The induction motor.

When mentioning high-voltage lamps, I do not especially refer to
the modern lamps of 200 volts and upwards^ut to the invention and
development of lamps with carbon filaments.

The mathematical treatment of the principles of the dynamo, and
the laws which were thereby laid down for its construction, was the
most important contribution to the problem of electrical engineering
which has been made.

1903.] OF MANCHESTER LOCAL SECTION. 559

By no means one of the least important points in the evolution of
the generator is the universal adoption of carbon brushes, which has so
greatly assisted to sparkless running and fixed lead. Various qualities*
of carbon have been introduced of different resistance and hardness ;
those of higher resistance and finer grain being found most suitable for
high-potential, and those of low resistance and coarser grain for low-
potential machines, for, as a rule, no one type of carbon is found equally
suitable for a large range or variety of generators.

Incidentally the development of the electrical generator gave a
strong impetus to the improvement of the steam engine, and the great
accuracy with which electrical measurements can be carried out has
been the means of enabling the steam consumption at all loads to be
definitely ascertained, and one type of engine to be readily compared
with another. This has led to the acquisition of much useful knowledge,
and to many improvements in design.

By the adoption of the three-wire system in place of a two-wire
circuit, the weight of the copper required to transmit a given power a
stated distance, with the same percentage of loss, has been very much
reduced, and during the last few years the introduction of incandescent
lamps for double the previous voltage has extended the scope of supply
on the three-wire system to such an extent that direct-current supply
has received a new lease of life, and the competition which at one time
existed in this country with the single-phase system has been to a great
extent, if not entirely, eliminated.

The series-parallel control for tramway work was one of the great
steps which placed electric traction upon a sound commercial footing.
By its adoption the units per car-mile were reduced by some 30 per cent.,
and the maximum current demanded from the station by approximately
the same amount, and the great reduction that this represented in the
first cost of the generating station and in the cost per car-mile is well
known to all engineers.

The induction motor, and the branch of electrical engineering to
which it is alUed, is the present day development of the alternating-
current systems. For many reasons three-phase machines have not
been so largely adopted in this country as in some others. The
increasing size of stations and the increasing need for placing them
further out has, however, given rise to an increasing demand in this
country for polyphase currents. But there is no rivalry between the
direct and polyphase systems ; each has its proper place.

A review, however superficial and short, of past progress may well
cause us to ask what degree of perfection have we arrived at, and what
may we anticipate for the future ? New discoveries and developments
generally tend to simplification, and the operations by which a given
purpose is effected are generally reduced in number as experience is
gained and as the problem dealt with is better understood. If this
could in any way be accepted as a law, a brief consideration of the
pwesent method of generating light would indeed prove that our
procedure is most primitive ; for it is evident, even to the most
uninitiated, that we obtain our light by an exceedingly roundabout
process, and that being so, we cannot expect that it should be highly

660 EARLE: ADDRESS AS CHAIRMAN [Manchester,

efficient or economical. A brief consideration will show the result
which is attained.

• Taking coal having a calorific value of 14,500 units per pound, and
assuming 9 lbs. of steam to be evaporated to 160 lbs. pressure per
pound of fuel, the efficiency of the boiler and cconomiser is, approxi-
mately, 72 per cent. An engine taking 13 lbs. of steam per I.H.P. has
an efficiency of about 17 per cent., or a combined efficiency with the
boiler of approximately 12 per cent. ; and, assuming the ratio of the
B.H.P. to the indicated power of the engine to be 90 per cent., we find
that the ratio of the useful return in B.H.P. to the heat units in the coal
is represented by 107 per cent. Now 7 per cent, of this figure is lost
in the generator, giving an efficiency of E.H.P. coal burned of 10 per
cent

The heat units in the coal have been very inefficiently utilised, but
what happens during the operation of converting electrical energy into
light ? From investigations which have been made in connection with
the energy consumed by an incandescent lamp, it has been shown that
only a small portion of the total radiation is luminous and capable of
a£Fecting the eye as light. Taking this portion as 5 per cent on the
average, we find that of the total heat units in the coal practically the
whole are dissipated, and only a remainder of ^ per cent, is converted
into the light which it has been our object to produce.

This small result obtained in return for so much coal burned is most
unsatisfactory, but how are matters to be bettered, and from whence is
improvement to come ?

It is evident that for the cheaper production of light by means of
the incandescent lamp we must look to improvement in the lamp itself,
for it is the most inefficient member of the system with which we have
to deal, and since its introduction but little appreciable advance has
been made in its efficiency. The production of light by the arc gives
a somewhat better return, the ratio of luminous to total radiation being
between 5 per cent, and 15 per cent, and the useful return from the
heat units in the coal burnt about i per cent.

When electrical energy is required for the production of power,
owing to the high efficiency of the electric motor, which is between
90 and 95 per cent, according to size, a net return of nearly 10 per cent,
is obtained, and in this case the greatest loss takes place in the steam
engine.

Besides the study of the efficiency of engines, generators, lamps,
and motors, there is in connection with our present generating stations
an item amongst the expenses, which all who analyse the published
returns well know varies between wide limits, and this is the cost of
fuel per unit generated. It might possibly be thought that these large
differences were chiefly due to the price per ton which has to be paid,
but investigation will show that, apart from any question of price, the
actual pounds of fuel burnt per unit sold or generated vary widely at
different stations, even though the quality of the coal may not vary
greatly and the load factor may be very similar.

The type and size of engine, the class of boiler, the load factor, and
the nature of the load, account for a great portion of this difference.

Ito3.] OF MANCHESTER LOCAL SECTION. 661

but it seems more than probable that there is, in many instances, a
large personal element involved.

Electrical generating stations for lighting and traction have for
some time been laid down on lines which have varied but little. There
is, however, a great development before us. Large power-stations are
about to be erected in various parts of the country to supply power
over large areas, and many of the larger towns are building, or are
about to build, very large generating stations. All those connected
with these undertakings are naturally only too ready to take advantage
of any new development, improvement, or invention which may assist
to further economies. Are any such opportunities offered to us ? Is
there any probability of the present reciprocating steam engine being
superseded, or can we look for improvement in the incandescent lamp,
which, owing to its present low cfi&ciency, is the most unsatisfactory
member of our lighting system ?

With regard to the former, two types of engines are now forcing
themselves upon our notice. They are the steam turbine and the gas
engine.

The steam turbine, in the able hands of its inventor, is now reaching
a degree of perfection when it can no longer be neglected, for it is not
only becoming the rival of, but for many purposes is actually threaten-
ing to supersede, the reciprocating engine. An engine in which the
moving parts are reduced to the miniinum cannot fail to be attractive,
and in the turbine, valves, eccentrics, and reciprocating parts are entirely
absent. The economies which have been effected in the steam con-
sumption of the turbine are due to a variety of improvements, but to a
large extent to the advances which have been made in connection with
it when running condensing. The design of the turbine constitutes it
a multiple-expansion engine, in which the steam can be expanded one
hundred- or even two hundred-fold, as compared with eight- to sixteen-
fold in the compound or triple-expansion reciprocating engine. To
this exceptional ratio of expansion the economy of the engine is to a
large extent due, and as the expansion extends over nearly the whole
range between the boiler pressure and that in the condenser, the effect
of a good vacuum is most important, and for every additional inch of
vacuum above 25 to 26 a saving of approximately 5 per cent, is obtained.
In the turbine there is no initial condensation, and therefore greater
gain by a good vacuum than in the reciprocating engine. In the latter
type of engine a function of good vacuum is a corresponding increase
of size of the engine so as to cope with the greater volume of steam,
but this is not so in the turbine, and on this account; in the turbine,
steam can be expanded to a limit which mechanical considerations
render impermissible in the reciprocating engine. In the average
reciprocating engine much loss is caused year in and year out by leaky
slide valves, and great loss is due to alternate contact of the inside of
the cylinder walls with cold exhaust and hot steam ; but in turbines, as
the flow is always in one direction, there are no periodic fluctuations,
and therefore none of the above loss. Besides the excellent results as
regards steam consumption in the turbine, it claims other advantages
of considerable importance. The first cost of the combined plant is

662 EARLE: ADDRESS AS CHAIRMAN [Manchester.

appreciably reduced, the necessary buildings are much smaller, and
the foundations inexpensive. No internal lubrication is necessary — the
saving on this account is considerable — and the condensed steam can
be returned to the boiler uncontaminated by oil, and without the
necessity for oil filters.

The second type of engine, viz., that using gas as the motive power,
has comparatively recently, owing to the greatly increased size in which
it can now be built, and the production by various processes of cheap
gas, won for itself a very high position, and one which is fully justified
by its performances, and it has established its claim as a competitor of
the best and largest steam engines.

The four strokes per cycle single-acting engine is that which in the
past has been commercially the most successful, but as the demand for
engines of larger and larger size has arisen, the disadvantage of only
utilising one stroke in every four for the generation of power, and the
necessity for two or even four cylinders for engines of no very great
power is tending rather to the adoption of one impulse per revolution,
or even one impulse per stroke.

Records exist in great quantity of gas engine performances, both
for the older and more modern types, but it is unfortunate that con-
fusion should be so often caused in their study by the envployment
of units based on different temperature scales and weights. Thermal
efficiencies are also calculated in two different manners, based either
upon the higher or the lower value of the gas, and by the existence
of three determinations of calorific value, and two methods of cal-
culating the thermal efficiency, the performance of an engine may
be presented to us in any of six ways. This in an outrage upon our
time and patience, more especially when one has frequently to search
through a whole book or paper to discover the units upon which the
results are based.

So long as gas engines were run upon town gas their field of opera-
tions was limited to comparatively small powers. But as the size of
engines increases, the efficiency of the steam engine rapidly improves,
while for the gas engine it remains more nearly constant ; consequently
the utilisation of high-priced illuminating gas does not admit of
economical working except for small powers. To enable gas engines
to compete with steam for the generation of power on a large scale,
a cheap and reliable gas is essential, and for many years inventors
have been working on this most interesting and important problem.
Apart from the question of producers, designed especially for the
manufacture of 'power gas, there are sources of supply which, when
available and turned to account, yield exceedingly valuable results,
and the utilisation of the gases from blast furnaces and coke ovens —
the great portion of which has up to the present been allowed to go to
waste — is a problem of the very greatest importance.

Excluding illuminating gas, which is too expensive for use in large
gas engines, natural gas, blast furnace and coke oven gases, which are
only occasionally available, three kinds of gas remain, which are named
respectively producer, water, and power gas.

Producer gas is generated by forcing a current of air through

1903] OF MANCHESTER LOCAL SECTION. 663

glowing coal. Water gas is produced by passing steam through fuel
which has been raised to incandescence by first passing a current
of air through it. The production of power gas is a combination
of the two processes, in which steam and air are admitted simul-
taneously, and though the resultant gas is poorer in quality than water
gas it is richer than producer gas, and the process has the great advan-
tage of being a continuous one.

Power gas was, during the early years of its manufacture, made
from anthracite or coke, and excellent results have been obtained, by
which a horse-powcr-hour is produced for about i lb. of coal, but lately
a process has been designed which enables the cheapest bituminous
coal and slack to be used and at the same time the ammonia to be
recovered as sulphate of ammonia. It is hardly to be wondered at that
this great advance in the economical production of gas has brought the
question of the utilisation of gas engines for the production of power
on a large scale into great prominence.

The relative working costs of gas- and steam-driven plants are
dependent upon the quality and cost of fuel which the type of pro-
ducer requires, and the cost of coal for the steam plant.

Briefly comparing a 400- H. P. steam plant with a gas plant of equal
power (the latter utilising gas manufactured from anthracite), we find
that a 400- H. P. compound steam engine, condensing, including boilers,
boiler-house and chimney., would involve a capital outlay of approxi-
mately ;£ 5,900. When working this plant for 3,000 hours per annum,
and taking the cost of coal at los. per ton, the total yearly cost, in-
cluding depreciation and interest on capital, would be £ifS7S' This
gives a cost per H.P. per hour of 0*325 pence.

Considering this against a gas engine, producer, and building, the
total capital outlay for the plant for the utilisation of anthracite would
be ;£4,5oo, and, taking the anthracite at 23s. per ton, the working
expenses would be ;£i475, or 03 pence per H.P. hour.

These figures relate to a plant in which expensive fuel is used in the
producer, and when considering the cost per H.P.-hour it must be
borne in mind that it is assumed the plants are running for ten hours
per day on full load.

With respect to producers for the production of gas from bitu-
minous slack, the cheaper fuel gives results which show a considerable
economy when gas plants of even 500 H.P. are compared with steam,
and without taking into account the question of ammonia recovery.
But when the power rises to 3,000 H.P., or thereabouts, and it becomes
economically advantageous to recover the ammonia, the value of this
bye-product reduces the nett cost of the gas to such a figure that, with
coal delivered at 8s. a ton, the nett cost of fuel does not exceed one-
twentieth of a penny per H.P.-hour. Such a result is one which points
to the certainty of the adoption of the gas engine for all large power
plants.

Besides the reduction of coal consumption by the aid of rotary
steam engines or of gas engines, there is the possibility of reducing
the cost per unit by improving the load factor. A large generating
station, with a tramway and power load may have a factor approxi-

564 EARLE: ADDRESS AS CHAIRMAN [Manchester,

mating to 20 per cent. If this could be increased to 50 per cent., costs
would fall by practically one-half. Storage batteries are the only known
means at our disposal for effecting an immediate change of this mag-
nitude ; large first-cost and the maintenance charges alone stand in
the way of their immediate adoption upon an enormous scale. We
are, in fact, waiting for the ideal storage battery. The destruction
of storage batteries is due to the continual expansion and contraction.
A cell with a life greatly in excess of anything yet produced is no
impossibility. Whether the iron, nickel-oxide battery, of which we
have heard, is to solve the problem of long life, or whether iron is to
replace lead, I do not know ; but iron is the cheapest of metals, and,
weight for weight, should yield a watt-hour output about the same
as zinc, and many times greater than lead, and if the initial difficulties
have been overcome this new departure in batteries will be of the first
importance. But it is well to note that a great length of life is not all
that is required, the first cost being as important a factor, for the
interest on any additional outlay must be charged against any saving
effected in yearly depreciation ; and, if the cost of the battery is
increased, in order that the yearly charges shall remain constant, the
life must increase as the square of the cost. Apart, however, from the
use of batteries merely for the purp>ose of storage, there is an immense
field for their employment as regulators in large power-stations.

Touching upon the question of •the supply of electricity in bulk for
power and other purposes, this is a subject upon which a war of argu-
ment has been waged, and the financial success of such undertakings
has been questioned. We may, however, leave this great question to
decide itself upon its merits, for several of the power companies have
already started operations. The power companies have been excluded
from giving customers a supply within certain town areas, with the
object of protecting the municipalities from competition, and although
the towns are at liberty to take a supply, or give permission to supply,
they as a rule do not at present look with favour upon these gentlemen
with roving commissions. Still, the effect of the companies, carrying
on operations outside their gates, will be felt, for low charges for power
will tend to attract small manufacturing firms to districts where rates
are low and land is cheap.

I have given some consideration to the question of the supply of
energy by power companies for the purpose of lighting small districts,
and have also worked out the savings that would be effected and the
extra expenses that would be entailed by putting in batteries of
sufficient size to increase the load factors from 9 per cent, to 20 per
cent., and the result of my investigations goes to show that the prices
which would have to be charged compare most favourably with those
charged by small companies having outputs similar to those I have
assumed. But the true object of the power companies is the supply
of energy for power, and for success upon a large scale all costs must
be cut down to the lowest possible figure. Hence such companies are
bound to give, as I have said before, consideration to the steam turbine,
the gas engine, etc. The cost of the electric light could also be reduced
by improvements in the lamp itself. At the present time the efficiency

1903.] OF MANCHESTER LOCAL SECTION. 566

of the lamp is such that the hourly cost of current greatly exceeds the
hourly cost of the lamp, for, taking the cost of a 60- watt lamp at is.
and its useful life at 1,000 hours, we find that at 4d. per unit the hourly
cost of current amounts to twenty times the hourly cost of the lamp.
This great difference between the two charges indicates that the lamp
should, on commercial considerations, be called upon to do more work
with a smaller expenditure of power, even if thereby its Hfe were
shortened. Many attempts have, of course, been made to produce
a substance capable of being run at a higher temperature than carbon,
and there is no reason why we should not look forward to an efficiency
which would at any rate halve, or even quarter, the present cost of
lighting. The mercury lamp may indicate the type of the future, but
at present the quality of its light is not such as would recommend its
adoption.

And now to what extent are our home firms in a position to take
advantage of home and colonial demand. I am convinced that we are
in every way able to hold our own in the competition, but we must not
fall into the dangerous error of hiding from ourselves the many
excellent features in the machinery of our foreign rivals. Looking
back upon the steady and continual progress which has been made,
and considering the great opportunities that are still open for improve-
ments in the various branches of electrical engineering, the many
applications of electricity which are only yet partially developed,
and its great future in connection with power-distribution and electro-
chemistry, one cannot help feeling with some degree of confidence
that the progress of the present century wilt equal, if not surpass,
that of the last.

566 DICKINSON :* ADDRESS AS CHAIRMAN [I^ds,

LEEDS LOCAL SECTION.

INAUGURAL ADDRESS OF CHAIRMAN,
By Mr. HAROLD Dickinson, Member.

(ABSTRACT.)
{Address delivered February jqth^ ^903.)

In electing me your chairman for the first year of the existence of
the Leeds Section of the Institution of Electrical Engineers, you have
conferred on me an honour of which I am justly proud, and for which
I thank you.

In the earlier part of my address I propose briefly to rehearse the
objects and advantages of the Institution, and with regard to the rest of
my remarks I have decided, after some thought, to leave all technical
matter to be dealt with in papers specially devoted to specific subjects
and to seek to lay before you the commercial and educational problems
with which, sooner or later, we shall have to deal. This I do in no dog-
matic spirit, but rather in the hope that, by pointing out what I conceive
to be imperial issues, an avenue is opened for their consideration and
discussion.

The Institution of Electrical Engineers was founded in 187 1 under
the title of the Society of Telegraph Engineers. It is the oldest and
largest Institution of electriqal engineers in the world. The Institution
has not only grown rapidly in membership, but it has grown in its utilit>\
Local Sections have been formed at home and abroad. Science Abstracts
have been circulated. Visits have been paid to foreign countries and
capitals — to Switzerland in 1899, to Paris in 1900, to Berlin in 1901, and
one will be paid to Italy this year, and another to America next year.
The Institution has also exercised its influence in regard to Board of
Trade Regulations, Factory Acts, and so forth.

I have indicated some of the lines on which the Institution has
moved in the past, but there are other duties that will be expected of it
in the future. The competition from foreign nations now being experi-
enced in the electrical industry necessitates the careful attention of the
Institution to all the problems relating to the progress of the industry,
which I hope soon to see having serious consideration, such as questions
of the management and conditions of workshops, conditions of labour,
education and fiscal conditions. These questions necessarily cannot be
discussed by an Institution of this kind with any view to interference,
but purely so that the best methods may be brought to the notice
of the manufacturers themselves and the representatives of labour, edu-
cation, and the public at large. Then the Institution may, through its
influence with the Colonies, be able to promote the interest of the
industry by making known to its Lo^aJ Sections all that is going on at

1903.] OF LEEDS LOCAL SECTION. 667

home and abroad. Further, the conviction I believe the Colonies have
that the electrical industry at home is in a worse state than actually is the
case, can easily be corrected through their own Sections.

As to the origin of our Local Section, I may remind you that it was
some nineteen years ago that the first efforts were made to form an
Electrical Engineering Society in Yorkshire. The movement, however,
fell through. Through the instrumentality of our Hon. Sec, Mr. G. R.
Blackburn, a local society has now become an accomplished fact by
the formation of the Leeds Section.

I should like to point out, now the Section is in existence, that the
responsibility of members does not end with the payment of the annual
subscription, and that, in order to make the Section a success, it is
necessary each member should take a keen interest in the work. I find
that the membership of the various Local Sections is as follows : Man-
chester 445, Leeds i8i, Birmingham i8o, Glasgow 175, Newcastle 140,
Dublin 65. It will be seen, therefore, that with regard to member-
ship, as compared with other Local Sections, we are very well off, and
it only remains for the members to put in a little of the enthusiasm they
instil into their profession to make this Section one of which the parent
Institution and the other sections will be proud.

Before coming to the immediate subject of the second part of my
address, I should like to call your attention to the phenomenal progress
which the industry in which we are all interested has made during the
last thirty years. In the early days Telegraphy was its mainstay, then
came Telephony, then Lighting, and then Traction, in which there is now
;£6o,ooo,ooo of capital invested. In regard to lighting, the enlargement
of the business has enabled the cost of production to be reduced, and
we may anticipate further reductions in the near future by reason of the
improvement in the load-factors due to a more diversified type of user.
The price at which electrical energy can even now be sold is such as to
place it within the reach of all classes.

One great reason why there is not a much greater increase is, I
think, the initial cost of wiring. Any steps taken to reduce this cost
must tend to the benefit of the business and lead to an increased use of
electric light as an illuminant.

We have all recently heard a great deal about the various power
schemes that have been formulated throughout the country. It seems
to have been assumed by many people that because a scheme is
designated a power scheme it possesses some merit which will enable
power to be supplied at very low cost, but the principles which go
towards the production of energy at low cost are apparently forgotten.
Unless a power scheme has a good load factor it seems hopeless to
expect low costs, yet in many of these cases the areas are immense and
the districts very scattered, which involve very heavy distribution
costs. I do not wish to say one word to discourage any scheme which
may benefit the industry, but I consider that, before the public are
invited to subscribe money for the development of some of the
schemes proposed, the facts should be very carefully weighed in the
light of our present experience of the factors which govern the cheap
production of power, for, if a number of these schemes are unsuccess-

YoL. 82. 88

568 DICKINSON: ADDRESS AS CHAIRMAN [Leeds,

ful, it will tend to shake the confidence of investors and thereby cause
a serious check to the industry.

What has already been stated shows very briefly how the industry
has advanced, and its continued advancement may be forecast
when we consider the number of new schemes for the future.

Our Position to meet Competition.

But, gentlemen, the consideration we have just given to the
development and prospects of the industry at once suggests the
question, ''To what extent are we equipped for meeting the future,
electrically and generally ? "

It will be admitted that commerce plays a very important part in
deciding the position that a country occupies among the nations of the
world, and, true as this is of our day, how much more so is it of the
future ? We must all appreciate this, and it is therefore incumbent on
us as a nation to study commerce and all things that tend to enlarge
and foster it. There are, of course, many avenues through which we
may study it, and this brings me to the crux of my address, and,
conscious as I am of my own limitations, I only deal with the subject
because I feel that the position of commerce generally, and the electrical
industry in particular, in the United Kingdom is not on the sound basis
we should all like to see it. The question before us is of vital
importance both to the producer and the user of electrical apparatus.
The magnitude of the problem is obvious, and I fully appreciate the
vast knowledge essential in order to arrive at a correct decision as well
as my own lack of that wide experience necessary for the formation of
any reliable opinion. But as to the lines of the question I am fully
convinced, and I content myself rather with suggesting those lines
than with the expression of any very definite opinion thereon. So
serious is this problem, not only to our industry, but to commerce
itself, that I am sure every one who has the welfare of the empire at
heart will feel that, whatever one's limitations, one is quite justified in
raising one's humble voice to swell the chorus now being raised that
serious, studious, and practical application may be given to the issue
before us.

There can be little doubt that, till quite recently, British capitalists
and manufacturers have dozed. The commercial habits of their early
days have been allowed to be the only habits that could attach to
business life. Precedent has been followed instead of new precedents
being established. Indeed, I suggest that precedent should be, com-
paratively speaking, a dead word, for a new precedent is scarcely
established before the environment of commercial life renders it
antiquated. A perpetual study should be given to the ever-changing
conditions of commerce, and business should be continuously adjusted
to these conditions. Fortunately, the commercial instincts of our day
have responded to the uneasiness, occasioned by the wonderful
ildvanccs of our commercial rivals, and the last few years have been
spent in good work whose fruit will assuredly be seen.

But it will be obvious that the question " To what extent are we

1903.] OF LEEDS LOCAL SECTION. 569

equipped for meeting the future ? " is not merely a question of our day.
It is one for all time. Each generation must ask itself that question.
Having asked it for our own day, let us proceed to examine it. It seems
to me the question must be examined under at least the following four
heads: (a) Foresight, (b) Management, (c) Education, {d) Fiscal
Conditions.

Foresight. — ^I'he consideration of foresight may be dismissed in a
few words. One instance of the want of foresight of our electrical
manufacturers may be seen in their neglect to lay themselves out some
years ago to meet the demand for the larger units required for central
stations, with the result that so many of the largest sets were supplied
by foreign firms. It is always easy to speak after events have passed,
but that this demand would arise for larger units was so absolutely
certain and so perfectly obvious to those who considered the subject
that it is astonishing to me that manufacturers should have allowed
themselves to be in the invidious position of seeing orders, which
ought to have been theirs, going out of the country.

In this connection I appeal to our moneyed classes to realise more
fully the dignity of commerce, to sink their money in ways that, if they
do not yield immediate prospects, will certainly show handsome future
returns. It is to these men we must look for assistance in the opening
up of new markets. It is of them we demand that instead of buying
up landed estates that yield but little either now or hereafter, they will
invest in that which will ultimately provide them an ever-increasing
yield and the nation with a hard-working, intelligent, commercial
community.

Management. — In considering this question we must do so in com-
parison with our competitors abroad. In the electrical industry it is, I
say, a serious reflection on our manufacturers of electrical plant that
the bulk of the orders for the largest schemes have gone to foreign
firms, or at any rate to firms of foreign origin. It gives much food for
reflection that to-day the purely English electrical firms, with perhaps
but one exception, are not in a position to take one of these large
contracts in competition with the large American or Continental firms,
for the simple reason that the English companies are too small. I do
not say that they could not execute the work from an engineering
point of view. I think they could, and certainly as well as (possibly
better than) the foreign firms, but I say that for financial reasons such
contracts are prohibitive to them at present, the risk with their
comparatively small capital being too great unless they could get the
contracts at their own prices, which must be liberal. They dare not
take such a competitive contract, for the reason that it would mean that
their works would be run almost entirely for one job, and in case of
any miscalculation they might be put into a very awkward position. It
is evident that our manufacturers are now progressing, but I am afraid
it must be admitted that it is not so much due to their desire to obtain
the best results, but rather to sheer necessity.

With regard to the question of labour, I think our inanufacturers
must, in their own interests, and in the larger interests of the nation,
study this question seriously. I know that blame is laid at the door of

570 DICKINSON : ADDRESS AS CHAIRMAN [Leeds.

the working man for restricted output, and often do we hear the men
criticised in this respect ; but is it just ? Is the blame all on one side ?
I say emphatically, No. I believe the cause of restricted output is due
to the system of payments generally in vogue. If you wish to* get the
greatest output you must pay for it. This, it seems to me., can only be
done by paying on a liberal scale on the bonus or premium system, or
some other system which will give an inducement to exert best
endeavours. If this practice were more general in England we should
see more of the close attention and the steady and consistent applica-
tion to the work on hand that is so marked in up-to-date workshops.
The greater security the manufacturer can show for the future
maintenance of the higher wage earning facility this scheme affords,
the greater will be the chance of the system becoming general, which
will be to the permanent advantage both of the manufacturer and the
artisan. It must be understood, of course, that in advocating this
attempt to obtain increased output, I am not advocating in any way
any lowering of the standard of quality of goods produced.

In addition to this, the workman should be induced by every means
to use his brains to suggest any new process or tool to facilitate greater
output, and to do this it will be necessary to compensate him for his
skill where it is found to be beneficial. I have often heard it said that
the British working man has no brains. I do not believe it, and 1
^ympathise with what he has said, by his actions, that he is not
prepared to give the manufacturers " something for nothing." If he
has brains he is capable of being influenced, and it is the duty of the
manufacturer to see that he is properly influenced, and this can be
most readily done by making it worth his while to try.

The last point I would mention under this heading is that of
advertisement. There can be no doubt that orders have gone to at
least one of our rivals because of what I will term his arts in advertis-
ing. These are not confined to the orthodox announcement in a trade
journal, nor to the apparently inspired leaderettes in the daily press
and the monthly magazine, but to his assiduous and ofttimes daring
approach to possible users by careful and attractively penned letters,
and by the ingenious ways — I was going to say bluff — of his represen-
tatives. I think we underdo advertisement as much as this particular
rival overdoes it, and suggest our manufacturers give more heed to the
subject. The moral I wish to point is that the British manufacturer
has hitherto been too modest in advertising, and that the time has
arrived when the excellence of his productions and his stereotyped
form of trade journal announcement shall not be his only means of
communicating his existence to the world. I suggest he give some
study to the subject of judicious advertisement and seize every
opportunity of acquainting possible buyers and the general public,
through the medium of the daily press as well as the trade journals,
with what he has done and is doing.

Education. — On this subject let me request you all to read anew
Professor Perry's inaugural address of 1900. Whilst I emphatically
disagree (not from any strained patriotism, but from reading and
observation) with the Professor's inference that British electrical

1903.] OF LEEDS LOCAL SECTION. 571

engineers are behind those of America or the Continent in skill or
aptitude, the re-perusal of his brilliant and practical " straight talk " is a
tonic we should all take periodically. But, as I pointed out in my
letter which appeared in the Electrical Times of the 20th December, 1900,
if the British engineers' theory is faulty and incomplete, the methods
adopted in our colleges and institutions must be faulty and incomplete.
Since then there has been a practical advance in general commercial
education, but the curricula followed are mainly on foreign lines.
I assert that we should be in the van of technical educational progress,
not followers merely. Those in charge of this important department
of our national activities should certainly have associated with them
representatives of every branch of engineering, and they should
formulate a British curriculum. The value of constant and intimate
association between technical schools and manufacturers cannot be
overrated. The need for such co-operation is growing, and, as the
benefits of the secondary schools go to the manufacturers, I am quite
sure co-operation will result in manufacturers helping the schools with
funds and plant.

Fiscal Conditions, — The question of our fiscal conditions is one that,
as I have already stated, I am not prepared to dogmatise upon. On
the one hand, keen competition and the necessity for tackling big jobs,
which leads to amalgamation and combination, often ends in trust
abuses, whilst, on the other, a mote of necessary protection may lead to
a beam of abuse. Yet there is no doubt the tariffs of foreign nations
are becoming vexatious and require much study.

As regards our specific business, I have been thinking the matter
over and have come to the conclusion that there is, in some measure, a
degree of excuse for the holding back of our wealthier manufacturers and
financiers from erecting big works and laying out extensive plant when
there is always the bogey over their heads that empires, which have
protected their internal trades by walls of tariffs, have free access to
sell over here their surplus at less than cost price, or undertake big jobs
at practically cost price, the which keeps their plant fully occupied and
has an obvious effect on their trading. The electrical work of to-day
and of the future renders big works absolutely essential. Our foreign
competitors when erecting such can always feel they definitely com-
mand their home markets and can compete on practically equal terms
in ours. Have our manufacturers always to endure this increasing
restriction abroad and still be weighted by not even having their home
markets secured ?

I fully appreciate and most earnestly sympathise with our British
artisan, and think everything should be done that can be done to elevate
and help him. But the question naturally arises : " Is it not possible to
cover the increased price of necessaries which might arise if we adopted
some measure of protection by the extra work this country would obtain
and the higher wages it might pay, and, at the same time, might not
other possible grievances be foreseen and foreguarded by systems of
bonus or profit sharing ? " It may be that the welding together
of the British Empire will largely reduce the poignancy of the ques-
tion of free trade as it stands to-day, but that is ^ matter of very

672 DICKINSON : ADDRESS AS CHAIRMAN. [Leeds, 1903.

considerable time, involving as it does the fiscal policies of young
nations.

Under this head, too, the question arises as to whether our Govern-
ment gives sufficient consideration to trade questions. We are agreed
that we do not want too much Government interference. But I am
heartily in accord with the movement now being mooted by eight
Chambers of Commerce that the time has arrived when we should have
a Minister of Commerce, whose duties should be initiative rather than
administrative, whose time should be absorbed in Ending openings for
trade and advising on all matters concerning the conditions of trade
abroad. In this direction invaluable work is being done by the Com-
mercial Intelligence Department of the Board of Trade. But, good as
is the work of this department, it only goes to prove the necessity of
its having a separate existence. The administrative work of the Board
of Trade is vast. What we need is some one who is free to initiate antf
who will be responsible for any neglect in this direction.

I hope r have made it quite clear that I advance neither the
doctrine of free trade nor that of protection. What I do assert is that
the question is a grave one, immediately demanding further study, and
I plead that pressure be brought to bear on those in high places at once
to collect and study the data necessary for arriving at a conclusion
to lay before the nation.

In conclusion, let me assure you I am no pessimist. If we have
not kept abreast of the times it has been for reasons that would perhaps
largely have led to others becoming lax had they been in our place.
The British manufacturer is a man with a level head and a lion's pluck,
and he has awakened from his slumbers. The British workman is a
good fellow. I tell you I have been all over the British Isles on the
one hand, and on the other hand I have visited many big works in the
principal towns of the United States, Germany, Austria, and elsewhere,
and, whilst allowing for the disadvantages of flying visits, I did not go
with my eyes shut, and I tell you that for solid good work we are
unrivalled. To this good property we are soon to add the advantages
of our new interest in Technical Education and the like, and if only
employers will devote themselves to the earnest, strenuous study of
inter-trade problems and can see their way to bring men to be paid on
results — and in no mean spirit — the prospects of the old country in the
future are as great as ever they have been in the past.

THORNTON: SYNCHRONOUS CONVERTERS.

673

NEWCASTLE LOCAL SECTION.

EXPERIMENTS ON SYNCHRONOUS CONVERTERS. \^
By W. M. Thornton, D.Sc, Member.

(Paper read at Meeting of Section^ December /, igo2.)

§ I. The growth of large schemes for the electrical transmission of
energy by high-tension alternating currents is probably the most
remarkable feature in modem industrial development. The success of
these schemes depends mainly on unfailing regularity of supply, and
this again on the stability of the electromagnetic system of generators,
line, and motors under all loads. Those responsible for these schemes
make very cautious experiments, the cost of misadventure is too great,
and the machines themselves are rarely available under all the conditions
necessary for a complete study of their behaviour. I had the pleasure
of making some observations of wave-forms on the synchronous motor
system of the Wallsend scheme, and these suggested that a more
detailed research into the working of the two synchronous converters *
in the college laboratory might add to our knowledge of the complex
reactions within the armature of this and aUied classes of machinery.
The research is entirely experimental. There are so many variables
that it is useless to attempt to construct a theory including all of them.
Steinmetz and S. P. Thompson have given analyses of the ideal case
in which the magnetism is distributed sinusoidally around the circum-
ference of the armature. But though, as will be seen, the generated
voltage wave-form at no load closely approximates to a sine curve, this
can only be obtained by a magnetic distribution which is not sinusoidal.
Kapp has considered the variation of output with relative breadth of
pole, showing that within practical limits the output is less for the same
armature heating when the poles are broader. In Table I., I quote his
figures for two cases, and have calculated corresponding values for the
machines used in these experiments, which are not specially-designed

Table I.

Type

Phase dis-
placement.

Sine
distribuUon.

Pole breadth -r pole pitch.

•61

•88

Single- (

phase J

conver- j

ter (

COS0= I

= 7

85
6o

88
81
73
63

80
70

83-6

70-5
62-3

541

¥^
67 ,

57*2 ^

Three-

COS^ = *I

134

138

144

160

phase
converter

= Q

= •8

J not cal-
) culated.

128
117

137
126

149
132

146
132

574

THORNTON : EXPERIMENTS OX

[Newcastle,

converters. The figures are percentages referred to the same machine
working as a direct-current generator for equal armature heating in each
case. In the last two columns are the values which might be expected
from the two machines used calculated in the same way as Kapp's.
The alternating current, i, which heats the armature to the same degree

as the direct, i„ is i= — ^-/„^' the values of q being given in Table VII.,
and from this relation the latter part of Table I. was obtained. The

results are not total efficiencies. The w.itts lost in the field, friction,
windage, and eddy currents are all omitted, but the results are instruc-
tive, as showing the variations in the principal source of loss of efficiency.
The comparative values of Table I. are plotted in Fig. i. Most of the
curves show that the relation between power factor and efficiency is
not linear, the curvature being generally upwards. The Scott and
Mountain single-phase curve is, however, the reverse of this, and in
both single and three-phase sets the armature heating is approximately
• K.ipp, Dynamos, Alternators, and Transformers, p. 476.

1902.]

SYNCHRONOUS CONVERTERS.

675

in inverse proportion to the power factor. The meaning of the curves
drooping towards the low power factor end is in these cases the loss of
efficiency due to change of distribution of the current in the armature,
and has nothing to do with the effect of the eddy currents in the poles.
§ 2. The object of the experiments was to find how the efficiency of
the plant varied with load for all conditions of excitation, to find any

J,
<

l!=R^

?^ 5 ^

«-! .

^ iS c
^ fe'£

.- o C/3

ta^ -
s * c

c O g

C w C/3"

'^ .£ 'I

^:5 rt £

C/3 « <

o fcu a J-

^^ •- 1-2 ^

£ ^^'^

;? 5 - ^-

> iS w o

" OC tn T.

^.£K 5
S J3 -c i

I 0^ k:^
<^ a J t:

discrepancies between the theoretical and observed losses, and to locate
the causes which would give rise to them. At the same time, it was
thought that records of the changes of wave shape might throw some
light on the nature and magnitude of the armature reactions. The
greatest difficulty in synchronous converter working being periodic

676

THORNTON: EXPERIMENTS ON

[Newcastle,

lb
%

3
lb

19Q2.]

SYNCHRONOUS CONVERTERS.

677

c
>>

o
•J

(x3

fluctuations started from irregular turning moments in the prime
mover, the first machine was driven throughout from a set of storage
cells. Fifty-two of these were used to drive a 9-kw. bipolar machine
(Scott and Mountain), the armature of this being ring- wound and pro-
vided with slip-rings, so that single, two, or three-phase current could
be taken and supplied to a 5-kw. machine (Holmes), also bipolar and
ring-wound in the same way. From the second converter direct
current was led through an adjustable liquid resistance. The field of
each machine was separately excited from the same cells. A direct-

678

THORNTON: EXPERIMENTS ON

[Newcastle,

reading Siemens and Halske wattmeter was inserted in the line in series
with a standard low resistance, from the terminals of which connections
were made to one strip of a double oscillograph. The other strip was
placed in series with a non-inductive resistance across the line terminals
in turn. The resistance and capacity of the cables connecting the
machines were always negligible. The general arrangement of the
connections is shown in Fig. 2. There is, it will be seen, a double con-
version of current, and one point of interest brought out by the experi-
ment was that the heating losses of the system could, by varying the
excitations, be moved from one machine to the other. The two

ttU>f(f!M.

Fig. 3.

machines were run up together from rest coupled by the cables alone,
and the load gradually thrown on. Throwing it on suddenly started
violent phase swinging in the second converter, which measured in one
case 50 deg. difference between the limits of the current wave positions, as
shown by Curve 22, Plate 11.-=' The highest frequency possible was 23
alternations a second. The first set of experiments was made to find
the relation between total plant efficiency and power factor. The

• Greater swings might have been observed, but whenever the amplitude
increased beyond the above limit, the oscillograph synchronous motor came
out of step.

1902.]

SYNCHRONOUS CONVERTERS.

579

obscr\'ations are given in the following tables, and the magnetisation
curves of the machines in Fig. 3. From the latter an estimate of the
saturation of the magnetic circuit may be formed. The reluctance of
the Scott and Mountain at full excitation is '004SS, and of the Hohnes
'OOS2y, and the lengths of the air-gaps are riscm, and I'oOcm.
respectively.

265

331 26.
32

•85

.31

i 29
[28
' 27

2<^'

34!
23 1

255

245

235

■^

"N,

{

1*4 1-6 18 20

Exciting Ctsrrmf. S. & M.

Fig. 4.

2-4

Table II. (Fig. 4).

Field of first converter varied. Motor field constant. Loss in motor
field, 330 watts. Motor output kept as nearly as possible constant.

First converter input.

Volts

71
72

75
75'2

74*5

28-5

27*5
263

235

22*5

F. C.

Speed.

i-.s.s

i,coo

1*62

1,000

170

9QO

i«5

980

1-98

950

2'IO

930

212

900

2*34

920

2-55

930

37
37
37
37
37
37
37
37
37

Motor input.

455 : 323

465 I 30

47*0 I 28-2

48-0 j 25-3

482
48-5
47-8
48-1
480

241

240

25-25

259
29-3

Motor out-

Effi-

put.

ciency
Z

W. Cos0

1,125 ; -85

8-2

246

1,250 90

72-4

253

1,225 ' '93 72-4

8-3

25«

I1I74 97 72*4

8-2

260

1,165 '99 72

8-1

26-1

1,134. 97 1 70*6 8-2

26-1

1,150 95 70 1 8-0

25-6

1,100 -89

69 1 8-0

247

1,074 76

67 1 7-8

235

It will be seen that the maximum efficiency is reached a little before
the minimum current.

580

THORNTON: EXPERIMENTS ON

[Newcastle

•95

•85

235
23

2a-5
22
^21-5

•S 21

t«J 205
20
19-5
19

18-5

17-5

^30

Q 28

••■■I* Y / / ■

1*5

2 2-5

Exciting Current. Holmes.

3'5

Fig. 5.

Table III. (Fig. 5).

Field of first converter constant. Motor field varied. Loss in first
converter field, 116 watts. With the same input as in Table I.,
the output and efficiency are less.

First couv

srter input.

Motor input.

Motor out-
put.

Effi-
cienc>'.

Volts.

F.C.

Speed.

F. C. V.

Cos0

A. 1 %

, 73

261

980 37

48-2

258

1,210

•97

7*4

1
22*6

25-8

990 3-29

485

24-5

1,180

•99

71-6

7*4

23-2

74*1

25*4

1,100 2-98

48-5

1,150

•99

706

7*3

23*6

74-2

25-2

1,010 1 27

23-5

1,129

i*o

7*1

229

1,030 1 2-5

^^0

237

1,104

•97

23-5

75*1

244

1,040 j 2-3

47-8

24-5

1,079

7-0

225

75*1

24-4

1,060 2-17

47*2

253

1,069

65-8

6-9

21*9

75-3

24-2

1,070 2*03

^7,

1,060

'S3

6-7

210

75-«

24-1

1,080 1*93

46-9

27-8

1,044

•8

6-6

20'5

75-«

24-1

1,090

1-83

46-2

1,034

6-3

19-2

75-«

24-1

1,090

175

30-I

1,024

6o-8

i8-4

75-»

242

1,100

1-67

45*5

31-1

1,019

59-8

178

1902.]

SYNCHRONOUS CONVERTERS.

581

■95

^ -9

•75

2 28 t*!

a8%

627%

26%

25%

-=3=-^

-^^0^^

2*0 25

Exciting Current. Holmes.

Fig. 6.

Table IV. (Fig. 6). ^

Field of first converter constant. Motor field varied,
motor kept constant.

Current from

Finsl converter input. Motor input.

Motor out-
put.

Effi-
ciency.

V.
71-4

A.
27-6

F. C.

Speed.

F. C. 1 V.

Cos0
•96

A.
91

%
26*4

940

3-6

46*2

i»255

71-4

950 3*2

464 1 27

1,234
1,189

•98

274

990 2-66

468 I 256

•99

672

9-1

28*0

73*2

25«

1,000 2-28

46 , 262

1,160

•97

647

9-1

27*6

25-8

1,030

2-0

45*2 ; 27-9

1,139

•90

61-5

9-1

264

25-8

25-6

1,040

44-8 1 30-0

1,109

•82

594

25-9

1,060

1-65

43'8 32-1

1,0891 77

24*9

582

THORNTON: EXPERIMENTS ON

[Newcastle,

The conclusion to be drawn from the above figures is that, as one
would expect, the efficiency is greatest when the power factor is unity,
whichever field is varied^ and it is of interest to note the close relation
between power factor and efficiency over a wide range of excitation
while the output is maintained constant. Plotting the square of the

9rK

So,

"^.

■^^

^"v.

ef^/cii

NCY

' 5/

Fig. 7.

continuous armature current against efficiency (Fig. 7), it is found that,
except at low magnetisations, they are proportional. At low excitations
the effect of the large idle-current component is evident. In order to
see whether the higher efficiency was maintained at all loads when the
excitation was adjusted for the minimum armature current found above,

Fig. 8.

1902.]

SYNCHRONOUS CONVERTERS.

sas

three more sets of readings were taken, shown in Fig. 8. The second
converter fields were kept constant in each test while the load was
varied. The improvement in efficiency obtained at light loads is seen
to be maintained at the higher.

§ 3. The next experiment was a variation of the last, the machines
being run under all conditions of excitation, and readings being taken
of all the variables, including the wave-forms of the line current and
voltage. The results with the calculated efficiencies are in Tables V.
and VI., and Figs. 9 and 10 are plotted from these. The number of the
curves refers to Plate II. The remarkable 'feature of the curves is
their sudden droop at loads which, compared with the ordinary con-

50%

45%

40%

§35%

30%

25%

ao%

/•

fi
1

— — ui

«?MAL EX
fER
DER

CITATION

••

1,000

WatU Output.

3.000

Fig. 9.— Single-Phase Converters.

tinuous-current output, are small. The reason for this appears more
clearly when the machines are worked from the main generator, wliich
being driven by a single-cylinder engme has an irregular turning moment.
It was almost impossible to reach high loads without the second con-
verter coming out of step, and the only way to obtain them was to
over-excite the second machine and so reduce the eddy-current losses
and magnetic-current fluctuations and gradually lower the excitation
as the load was increased ; even then the machine soon worked up
a phase swing and came put of step. Fortunately, both armatures
have considerable inductance, about -002 henry, between the slip-
rings, single-phase, and there were no Ul effects beyond the racing
of the first machine. This was the first intimation, as a rule, that the
second had broken step, and it was always necessary to keep some one
by the main switch of the first machine to break the current before
the armature had accelerated to destruction. The advantage of normal
excitation is most marked at the higher loads in both Figs. 9 and i J.
Vol. 82. 89

584

THORNTON: EXPERIMENTS ON

[Newcastle,

Table V. (Fig. 9).

Single-Phase Converters, Variation of Load with excitation constant.

Field Currents : First Machine, 2 Amperes ; Second, i'93.

(Second, Under-excited.)

9
10

First Converter
input.

73 I 31

722 40

755 ! 505

71 I 62

80 I 71

692 40

II I 77 ! 81

2260
2890
4^50
4400
5680
2768
6240

Second Converter input.

Second Converter
output.

Arm.iturc
Efticiencics X

464

442

1400

464

1976

43-6

.63

2640

2948

845

3768

482

1864

412

3944

Coe0

•68

13-4

•83

227

•96

322

•99

•92

22-5

W istc. 2nd c. Total.,

710 62 1507 287

1 1 80 687
1780 695

1950 67

2494 66-5
i2i5|67-4

2600 63 -2

59« , 383
67-5, 44

66 42*2

657 1 420

65 410

66 140-5

Field Currents : First Machine, 2 Amperes ; Second, 272.
(Second, Normal.)

2630 466

1840

i*o

1875

1275

3620 46

2620

2875

1925

805

4900

496

3464

355

2550

725

100

7250

120

4348

465

2880

70 1 693 '437

71-2, 73*5
707 1 73*6

49
49

60 1 664 38

Field Current : First Machine, 2 Amperes ; Second, 3-29.
(Second, Over-excited.)

16
17

71
75
78
75

56
50

40
49
72
80

2840 1 46
3660 [ 47
5616 \ 465
6000 1 432

44 1 2000 : ro i 687 ; 1875 1275

56 2636
84 1 3856
95 14008

1*0 705 257 1820

•99 70 , 365 ' 2560

I I i

•98 65 I 385 ^ 2500

702 16375 395 J

717 1 69 , 45 I

685 695 1 42-5 j

68 613' 395 i

Field Currents : First Machine, 16 Amperes ; Second, 27.
(First, Under-excited.)

40
44

2240 44 1 45

1500

561 157

885

2200 32 i 50

1500

•94

505 17' I

865

67 ; 59 360
68-2 1 57*6 ' 360

Field Currents : First Machine, 3-1 Amperes ; Second, 27.
(First, Over-excited.)

19 63-5 33 2260

20
21

76 455
71 575

3460
4080

77 72 5540

42
46

405
43

47 1480 1 75 566 15-5 . 875 655 J 597 I 32-5

57 2400 ; 92 61 275 1 1675 695 i 70 ! 428

70 2860 1 ro 152-2
88 '3880' 1-0 ' 55

I
385 j 2010 70 I 68 1 445

50 1 2750 ' 70 , 71 460

1902.]

SYNCHRONOUS CONVERTERS.

585

^^^

—

^'"^

-*.^

/ /

SS i

/
/

1
1
1

wAm

ourm/r

Fig. 10.— Three-Phase Converters.

Table VI. (Fig. xo). — Three-Phase Converfers.

Field Currents : First Converter, i'9 Amperes ; Second, 3*62.
(Second, Over-excited.)

> First Converter
a 1 input.

0 '

Second Converter input.

^•|v.

Ac
36

W Co«0

23 75

2700

1794

•75

, 79

3470

45*2

2480

•74

24 «5

.54*5

4630

3352

•75

25 81*5

5620

4122

•75

26 77

82-5

6350

406

4650

•75

Second Converter
output

Armature
Efficiencies.

30
31

78
84

77
71

198
27

3475

475

58-5

1500
2106
2920
3660
4160

.stc.

jndc.

Tolal.

66-5

83-6

714

«s

60-5

72-5

»7-2

753

887

<)5

735

89-5

65-5

Field Currents : First Converter, 1-9 Amperes ; Second, 2*4.
(Second, Slightly Under-excited.)

37*5

2815 1 43*2

2472

1480

. 70

32201 39

353

2480

•98

1848 77; 74*5

755

435

4050 42

2950

•96

2485

727

842

4690 37*5

,52*5

3175

•94

2914

677

6320 65

4210

•91

58-5

4030

667

52*5
57
60

63
637

Field Currents : First Converter, i '9 Amperes ; Second, i '95.
(Second, Under-exdted.)

68 39

655
69

525

66-5

2650
3440
4580

5174

37*5 33 12600 1 10
365 43 ,3200,10
545 4160! 10

361
33

67 4370 96

635

21-3

1350

50*9

1972

93 617

57*3

2870

62-6

595

3090

707

597

686

THORNTON: EXPERIMENTS ON

[Newcastle,

§ 4. To illustrate the difference between theoretical and actual losses
Table VIII. was prepared. The heating was calculated by the formula
Pu=sq rCj q having the following values, and r being the resistance
per radian of armature circumference : —

Table VII.
Values of q.

First Converter.

Second Converter.

Single-phase.

Three-phase.
174

Single-phase.

Three-phase.

* =

1-285

1-375

17s

COS ^ = I

= 7

14-11
1982
25-27
3352

3-85

4*37
5-6i

ir99

i8-55

22
30

4-62

■ S-6i

Table VIII.
Watts Lost in Armature.

Single-phase

First Converter.

Second Converter.

CaL

Obs.
860

CaL

Obs.

915

225

955

914

435

796

1,121

1,510

650

760

1,585

M50

876

998

2,120

1,910

1,150

i.*94

745

904
2,296

348

649

2,720

1,440

1.344

531

790

205

565

995

1,000

475

695

1,520

1,536

725

914

4,100

2,902

1,260

1,468

655

820

200

72s
816

982

1,044

2,175

1,760

1,290

2,715

1,992

890

1,508

1,160

740

255

6t5

891

700

304

635

805

780

250

60s

1,000

1,060

850

725
850

1,350

1,220

2,120

1,660

1,440

1,130

Three-phase.

First Converter.
Cal.

318

475

727

1,165

1,685

190

297

272

620

1,015

212
380
614

913

Obs.

906
996

1,278

M98
1,700

343

740

1,100

1,515
2,100

50
240
420
840

Second Converter.

Cal.

Obs.

107

294

202

374

333

432

625

462

952

490

992

140

632

226

565

261
180

1,250

200

1,228

378

1,290
1,280

607

Values of r, ohms per radian.
First Converter, '036 (S. and M.).
Second Converter, '0446 (Holmes).

1902.] SYNCHRONOUS CONVERTERS.

587

Fig. II.— Second Under-excited.

fyoao

3^00

! ^

^/lOO

jSoa

//)ao

&»

S.M,

^ h»775 (?i/r/vr

^ '

Sooo

Fig. 12. — Second with Normal Excitation.

588

THORNTON : EXPERIMENTS ON

[Newcastle,

The general differences between observed and calculated losses
may be better seen from Figs, ii to 17, drawn Table VIII., the former
being shown by full lines, the latter by dotted. In all the curves the
ordinates are armature loss in watts, the abscissae output of each
machine. In the single-phase tests the first converter losses were in
most cases in excess of those in the second, but the difference between
observed and calculated loss was greater in the second than in the first.
The three-phase curves are more remarkable. In Fig. 15, which refers
to over-excitation of the second machine, the differences are much less
in this than in the first. Fig. 16 at nearly normal excitation shows
a reversal, which is more strongly marked in Fig. 17, where the second
converter field is very weak. The inevitable conclusion from this last
set is that the armature reaction harmonic is of sufficient strength to

Fig. 13. — Second Over-excited.

disturb the whole circuit, so that the magnetism is rapidly weakened
and strengthened in the solid magnet frame sufficiently to cause con-
siderable loss of energy, and that a change of excitation in the one
machine can cause a disproportionate change in the losses of the other,
unless by skilful design and the use of damping coils these fluctuations
in the magnetic circuit are minimised. In comparing these machines
with motor-generators, it should be remembered that there are similar
disturbances in synchronous motors. Beats can always be heard, and
each of these means a loss of energy by eddy currents in the iron of
the magnetic circuit. In F^ig. 18, I have drawn from Tables V. and VI.

• Vide Kapp. loc. cit. p. 475.

1902.]

SYNCHRONOUS CONVERTERS.

589

the separate efficiencies of the machines for three-phase working, in
which again there is a remarkable effect. The efficiency of the first
converter when the second is under-excited falls instead of rising with
tlie load, as much as i8 per cent, in one case, its own field being main-
tained constant. This again points to an abnormal increase in the

]^a»

Fig 14. — First Over-excited.

2m«

4<M1

-7SM.

hoc
Sit*

.^'

•
/

^^^^

■ — y

.^ H.

""^Z^

►v^fia

o*jrm/r

Zooo 3ooo

Fig. 15. — Over-excited.

Uooo

eddy-current losses. There is also a curious drop in curve I3, which
indicates that the sudden loss of total efficiency shown in Fig. 10 for
under excitation takes place in the first converter. It remains, then, to
prove experimentally that these losses are caused by armature reaction,
and to estimate their magnitude.

590

THORNTON : EXPERIMENTS ON

[Newcastle,

§ 5. I have worked out in a former paper * a numerical example of
the losses due to eddy currents in magnet cores. These can be cal-
culated when the dimensions and conductivity of the core and the
ampere-turns producing the change are known. Thus if c be the
radius of the core, / its length, ft the permeability, p the specific resist-
ance, / the frequency of alternation of magnetism, and (IT) the

ISoa

Zoa

/Sbo

/06C

Sbc

A>oo

Zooo Sooo fooo

Fig. i6.~Slightly Under-excited.

^000

Jk\.

/OOC

SCO

.M.

,^--^"

.*»-'^*''

MM77S

ourmn.

1000

Zcoo Jooo " J^o

Fig. 17. — Under-excited.

maximum value of the ampere-turns causing the change — this being
sinusoidal — then to a first approximation, the watts lost f

• •'Rotary Converters and Phase Swinging." The Electrician^ Sept. 27
and Oct. 4, 1901.

t Heaviside, Electrical Papers^ vol, i. p. 353.

1902.]

SYNCHRONOUS CONVERTERS.

691

To apply this to explain the difference between the observed and
calculated losses it is first necessary to know the ampere-turns of
armature reaction for any given condition of working. This was first
done in these experiments by placing a hot-wire galvanometer across
the otherwise unused series windings of the Holmes machine, these
forming an exploring coil of 58 turns. About one volt was observed
when running light, and photographs were taken showing the influence
of phase swinging on the magnetic circuit when unprovided with
damping coils. It occurred to me later that this voltage is sufiicient

•

V ^

Vi*.

-TL.

—It

^1I».

.X*.

' /

JL^ 9umHrcf uMomm otarmo.

TPUTorSteONO CONVERTER .

Fig. 18.— Variation of Efficiencies — Three-Phase.

to give good readings using the oscillograph as a dead-beat galvano-
meter, and I ran the oscillograph motor at the same time to see
whether the harmonics of armature reaction could be directly
observed. The results are shown in. Plate I., the corresponding con-
ditions being given in Table IX.* These curves are records of the

• The letters N, E ; U, E, etc., in the top row of numerals indicate the
excitations of first and second converter respectively for each vertical
column of curves.

592 THORNTON: EXPERIMENTS ON [Newcastle,

rapid magnetic changes occurring within the core when this is worked
at various saturations and with different values of armature reaction.
They are, in effect, the voltage in the secondary coil of a transformer
of which the magnetic frame is the core and the armature the primary.
They are interesting, as showing, for the first time, I believe, what
kind of action really goes on within the magnetic circuits of these
machines, and, I have reason to think, of all kinds of dynamo-electric
machinery, for I have obtained similar curves (Fig. 19) from con-
tinuous-current motors separately excited, driven from cells, and
running light. The most curious point, I think, about the curves is
the absolute constancy of form observed, except when a phase swing
starts. All the ripples remain steady, and the curves can always be
repeated. The same applies to the records of Plate I. This method
of examination seems to me to afford a most delicate test of whether
the armature is perfectly symmetrical in the gap, and should be

OeNERATED VOLTAOC

1120 R.RM

.-?'^y.'!!?.J. - - '^-^"'^^ -L /r' ^ WfTH I HELD

COIL VOLTAGE f \ ^ / 5.4 AMP&/ CURRENT

Scott & Mountain.

COIL VOLTAQg s/ M? W W V ^ 3* " ' CURRENTS

Holmes.

GENERATED VOLTAGE

Fig. 19.— Oscillations of Magnetic Fluids, in Separately Excited Continuous-
Current Motors Running Light.

useful in the study of flicker, or to indicate the magnitude of the dis-
turbances, mechanical or magnetic, caused by the armature running
out of truth. The records of Plate I. are no doubt complicated by the
presence of these oscillations, especially the more rapid movements in
the three-phase curves.

A detailed analysis of the curves in Plate I. would be very laborious,
but some general conclusions may be drawn. Taking the first converter
single-phase set first (curves i6 to 20 in Plate II.), it is seen that the light
load losses are practically the same for all excitations, and that over-
excitation more than doubles them for the same load, for the ampli-
tudes of the curves are much the same, and the strip resistance was
i6*i ohms in 16, but only 6*1 in 20. The first three and 20 show a
change of phase of the harmonic of about 45 deg., backward in 16, 18,
and 20, forward in 17. Under-exciting the first machine causes the
harmonic to lag with respect to the voltage more than in the other
cases. This double frequency harmonic alternately weakens and

1902. J

SYNCHRONOUS CONVERTERS.

593

strengthens the flux in the gap, and this can be seen by 19, where
it is in the first half opposite to and in the second in phase with the
voltage. The motor reaction, curves i to 5, shows a remarkably con-
stant type ; there is a quadruple harmonic present, and the phase of
this is moved i8o deg. of its own between 3 and 5. The reason for the
existence of these still higher waves and the meaning of this shift of
phase I have not had the time to examine more fully,* but it is of
interest to see that the same changes occur in the three-phase curves,
and that, as before, the losses are greatest with an over-excited first
converter.

Table IX.

Curve.

Single-
phase -
(Holmes)

3
4
5

Three-
phase
(Holmes)

' 6

9
10

Three-
phase
(Scott
and
Mountain)

' II
12
13
14
15

Single- /

' 16

f>hase

Scott K xu

and 1 1 19

Mountain) \^! 20

ist conv.

and conv.

Field

Current.

Current

1-93

272

329

3*1

1-9

362

2*4

1-95

3*1

362

1*9

2*4

1-9

1*95

1-6

3*1

3*2

1-6

1 3

Total ohms in strip

2nd conv.

circuit.

Con. cur.

Revs.

output.

Light.

Loaded.

1
!

2I'I

2I-I

1,150

211

2I-I

1,000

34*5

23*1

i»o75

13-1

23-1

1, 000

3i'5

29-1

33*1

1,020

3*1

4*1

1,000

417

4*1

1,020

4*1

6-1

1,000

2*1

1,000

III

1,000 ,

1
900

39*5

2*1

8-1

1,030

4*1

1,000

2*1

1,050

2-1

1,000 1

4*1

161

1,060

4*1

141

1,080

4*1

1,060

non-p.

6-1

1,060

15/25

6-1

840

To return to the determination of the ampere-turns of reaction.
Let t%be the voltage generated in the exploring coil, as found by a hot-
wire galvanometer or from the curves, and let there be s turns on the
coil. Then, when / is the frequency of oscillation (which will not be
simply that of the machines if there are harmonics),

er = 4 N/s/io*,
• It varies with both excitation and load.

694 THORNTON: EXPERIMENTS ON [Newcastle,

where N is the mean flux through the coil. Here e is root mean square,
and N an ordinary average, hence the true value of

N = 4-.'^.io«.
4/s 707

but s is 58 on the Holmes machine, 55 on the Scott and Mountain, and
/ and e are observed ; thus N is known. Now, N = Magnetomotive
force/reluctance. Thus writing

XT 4 IT I / . . X ,, N R

N = i- — -, the ampere-turns 1 / =

10 K* * 1 257

The maximum value for sine waves is 1*57 times this. Therefore

(IT)=r25NR.

For the Holmes machine, R = '005, as found from the magnetisa-
tion curve for 27 amperes, so that

(It) = 2,420^//;

and when the speed is 1,000 revolutions per minute,

(I T) = 146 per volt in the exploring coil.

For this machine the mean length of solid iron core is loocm., the
radius 7*8cm. Taking the specific resistance as 10,000, and the per-
meability as 100, the watts lost at 1,000 revolutions per minute are
I2S per 100 maximum ampere-turns.* Thus we have finally, since the
loss depends on the square of the reaction ampere-turns, 266 watts per
volt. Considering the double frequency harmonic, this loss is reduced
from 266 to 65 watts. When there is little or no phase swinging, the
voltage is from two to three at medium loads. The oscillograph cali-
bration was 2' I cm. deflection per volt with lo'i ohms in circuit, from
which the amplitudes of Plate I. may be worked out in volts.f Taking
an equivalent sine maximum of 2*5 volts, with the double frequency
harmonic of Curve 2, there are 102 watts lost by eddy currents in the
magnet core. It will be seen from Fig. 12 that this accounts for a good
deal of the discrepancy between the observed and calculated loss in the
Holmes machine, and I think that all the wide differences are due to
the same cause.

§ 6. Effect of Armature Reaction on Wave-Form, — ^The relation
between excitation and phase displacement has been shown in
Figs. 4, 5, and 6. These were verified by direct observation in the
oscillograph and the waves sketched. The voltage curve remains
singularly constant in shape under all conditions, but the current
wave, depending as it does on the phase relations of the two machines,
is very sensitive to changes in the magnetic circuits. The chief cause
of the variation of form is the harmonic of armature reaction, and the
phase of this changes considerably with regard to the main wave.

• Magnetic leakage reduces the intensity of the eddy currents towards the
yoke, thus diminishing the loss, but the working permeability is about 400,
and the eddy current loss is directly proportional to this.

t The curves as printed arc about quarter full size.

1902.]

SYNCHRONOUS CONVERTERS.

595

Plate II. contains a selection from the wave-forms sketched. The
current curves of Plate II. are not all to the same scale. Tables V.,
VI., and IX. give the true values. Curves i to 22 a are for a single-
phase working, the rest for three-phase. On all the curves but 22 and
22.\ the conditions of excitation are indicated by the letters O E, U E, or
N E, signifying over, under, or normal excitation. In 14A the phase dis-
placement from lag to lead as the excitation is increased in the second
converter is shown ; 22 gives the magnitude and nature of the wave
changes during moderate phase swinging, and 22A is the single curve*
in which the brushes have been moved from mid-position, A„ corre-
sponding to a slight backward shift, and A, to the extreme backward
shift when the sparking was too heavy to be long continued. The first
set, from i to 6, were taken after the readings of Table IV. These
were approximately repeated, as in Table X., to which the curves
correspond. In these the full effect of change of excitation can be
seen both on form and phase. The strong harmonic of Curve i always
appears when the second machine is fully excited and the field of the
first gradually reduced, the speed being maintained constant by
varying the armature current. The lateral shift of the harmonic is
most marked from i to 2, the other curves showing chiefly a variation
in its amplitude.

Table X.
Field Current of First Converter, 2 Amperes ; Second, 37 Amperes.

No. of •
Curve.

First Converter
input

Second Converter input.

Second Con-
verter output.

Cos0.

I
2

54*5

13-6
40

532
2,190

•65
10

19*5

Field Current of First Converter, 2 Amperes ; Second, 7 Amperes.

3
4

357

39*5

1,910

13-5

52-4

20*5

472

•44

19-4

Field Current of First Converter, 2 Amperes ; Second, 2 Amperes.

16
30

45*6

37*5

504
1484

•35
•87

o
61

Curves 7 to 21 were taken simultaneously with the readings of Table
v., as indicated, and it is of interest to trace the nature of the change
with load in each case of excitation. In 11, for example, the current
being more than double that of 7, the harmonic has moved over 60° and
its amplitude increased.

696 THORNTON: EXPERIMENTS ON [Newcastle,

The curves from 23 to 40 are for three-phase working, and partly
correspond to Table VI. In the last eight the first machine was driven
mechanically by belting, but the differences between these and the pre-
vious nine are not important. It is evident that the field distortion is
extremely small when working three-phase compared with single-phase.
With the exception of a weak third, harmonics are almost absent. There
is a slight distortion of the field as in a continuous-current motor, which
is met in practice by suitable brush displacement, but phase-swing is
difficult to start, and is not maintained to the same extent as in
single-phase running.

It may be concluded from these experiments that over-excitation of
the second machine or motor improves the stability of the system, but
that if the generator or first machine is under-excited, although the ratio
of the flux densities in the gaps may be kept constant, there will be both
an increase in the eddy-current losses and in the instability of working by
reason of phase swinging. It is more economical then to expend energy
in over-excitation than to allow phase swing to start and stop it by
damping coils. These are necessary in any case where there is
a periodic irregularity in the generator speed, but they depend upon
a well-marked change in the magnetic circuit, and when this is saturated
the magnitude of the disturbance is less.

Eddy currents in continuous-current machinery have been previously
thought of as almost entirely located in the armature and pole-faces.
From these tests it is seen that with a periodic oscillation through the
whole magnetic circuit the losses in the solid cores are considerable,
and I believe that the greater part of the eddy-current loss found by any
of the usual tests takes place in the solid frame. If this is to be prevented,
the mechanical construction must be as accurate as in engine fitting.
The pole-faces must be bored smooth and set to gauge. The armature
must be as true as a gun barrel and perfectly centred. Its shaft must be
stiff enough to prevent the least bending and must not whirl at any
speed, for the most violent magnetic changes will be set up if this occurs.
If it is attached to overhung pulleys or flywheels, which cause bending,
these must be compensated as in a balanced engine. Of course, all this
is if it is worth doing. It is merely a question of first cost — the user
pays for the energy lost in the damping system.

I hope that these experiments will be preliminary to others on sub-
station machines under working conditions, and a rather lengthy scries
of tests on the effect of brush position on efficiency and wave-form has
already been made. I think it will be admitted that our e.xpcrimental
knowledge of the reactions in alternators and converters, and in
continuous-current machinery also when subject to changes in the
mechanical torque, is at present imperfect. I venture to hope that the
experimental methods of studying the changes in the magnetic circuits
given in this and last session's paper * will contribute a little to a more
thorough knowledge of what really goes on within both fields and arma-
tures of dynamo-electric machines in general, and lead to an improve-
ment in their efficiency and stability of working.

• The Electrician^ May 30 and June 13, 1902 ; the Electrical Engineer^ April
and May, 1902.

1902.] SYNCHRONOUS CONVERTERS : DISCUSSION. 597

Mcr John H. Holmes (Chairman) said that the Institution was highly Mr. Holmes,
favoured to have had such an important paper read before it.
Dr. Thornton's previous paper had been of very great interest and this
was a continuation of it, while the points he had now brought out were
very interesting. It had probably been recognised, to some extent, that
changes took place in the field magnets of continuous-current dynamos
when there was something wrong with the armature, if it was very
much out of balance, or if there was a short circuit, but we had no idea
as to what those changes actually were. The methods introduced for
detecting changes in these magnets were very ingenious, and seemed to
make the thing much clearer. The question of rise in voltage on field
coils of dynamos had certainly been observed and had led to inquiry.
It was quite possible that the extraordinary rise in voltage noticed on
shunt windings when the armature was very much out of balance, or
what the Americans call the " bucking " of dynamos, might find some
explanation in this paper.

Mr. G. Ralph, after congratulating Dr. Thornton on his excellent Mr. Ralph.
paper, said that, unfortunately, his knowledge of the subject was so
slight that he could not criticise any portion of the paper, but he had no
doubt that many others, like himself, had occasionally in the course of
their work, met with some phenomenon which was puzzling at the
time, and for which they could not find any explanation. Cases like
these should be taken to friends like Dr. Thornton to be solved.

It might be interesting to them to describe a curious effect which came
under his notice a few years ago. He was engaged in carrying out
some efficiency trials of direct-coupled engines and single-phase
alternators at a Corporation Supply Station in the South of England.
The conditions were as follows : — The engine was a double-cylinder
single-acting engine. The revolving armature was of the disc type,
with no iron in it, of the well-known type made by Siemens, Ferranti,
and others. The alternator field was separately excited. When the
machine was running with no current in the armature, the potential across
the exciting terminals of the field was 80 volts, and the exciting current
agreed with this potential difference and the resistance of the field.
When, however, load was put on and full current was flowing
through the alternator aimature, the potential across the exciting
terminals rose 50 per cent, or more, although everything remained exactly
the same as before, that is, the speed of the alternator and exciter was
unchanged, the exciting current and resistance in the circuit remained
unchanged and yet the mere fact of putting load on the alternator
caused the exciting voltage apparently to increase to this degree. When
this was first noticed it was concluded that the voltmeter had gone
wrong. It was an electro-magnetic type of instrument. This was
taken off, and a Cardew hot-wire voltmeter and also a Kelvin multi-
cellular electrostatic voltmeter substituted with exactly the same result.
A similar effect was noticed the following day on the trial of a smaller
alternator. When he returned to the works after these trials were over
he tried to get the same effect on other alternators in the place— at
the time in the course of construction — ^and failed utterly. Some doubt
was then cast on his figures, and the engineer in charge of the station

THORNTON: EXPERIMENTS ON

[Newcastle,

Mr. Ralph,

Mr.
Hcaviside.

Mr. Eugene-
Brown.

IV.
Thornton.

where the efifect had been noticed was written to and asked to try again
and his (Mr. Ralph's) figures were repeated every time. He would like
to ask Dr. Thornton if he thought an effect like this would be produced
by armature reaction causing a very strong fluctuation in the field
magnet cores. He believed that in these particular alternators the field
was fairly weak, which, as pointed out in the paper just read, would
magnify any evil of this sort. He had never heard a satisfactory
explanation, and thought it might be interesting to mention the case.

Mr. A. W. Heaviside then proposed a vote of thanks to Dr. Thornton,
and in suggesting a visit to the dynamo room of the college, said it
would be very profitable to see the actual experiments.

Mr. E. Eugexe-Brown seconded, adding that he was well acquainted
with the subject itself, and was sure the experiments with the oscillo-
graph would be full of interest.

[The members then proceeded to the dynamo room, where Dr.
Thornton went through and explained the experiments, and also
answered the questions which were put to him.

The discussion was continued informally in the engine room while
the experiments were being shown. The curves of Plate I. were pro-
jected from the oscillograph on to a screen, and the change from one
to the other condition made gradually by the field rheostats. Periodic
movements in the curves, due to phase swinging, were started by
throwing load on and off the second converter. Messrs. Holmes,
Heaviside, Snell, and Ralph took part in the discussion, and in reply to
them the following points were brought out by Dr. Thornton : — ]

Dr. W. M. Thornton : It is not possible to prevent armature reaction
itself, and it is therefore necessary to check, in every possible way, the
communication of disturbance to the magnetism. This may be done in
any machine by damping coils surrounding the poles, by preference,
close to the armature. These act most efficiently when the iron frame
is solid, and depend chiefly on the eddy currents started by magnetic
waves sent radially into the core by the strong cun-ents induced in them
by slight changes of magnetism. Since they are useful even when the
iron is laminated in making any oscillation more dead beat by opposing
the initial change I would advocate laminating the magnet frame of con-
tinuous current machines ; for, in the first place, it would diminish eddy
current loss. It is generally taken that the no-load eddy current loss,
which can be found, remains substantially the same at all loads, but
according to these curves this loss is about twice as great at full load in
the second converter. In cases of parallel running, with compound
traction macliines for example, the currents in the equaliser circuits, and
therefore the voltages would more quickly adjust themselves. Design
in general is simplified by the accuracy with which the permeability of
these plates can be found.

The value of amortisseurs. in preventing fluctuations is such that one
may reasonably forecast the time when every large machine, either
continuous or alternating, will be fitted with them, for though by the
use of high-speed engines and turbo-generators, irregular turning move-
ment i:> less, yet the governing of both is far from perfect, and with the
small moment of inertia of the latter, sudden or periodic load

1902.]

SYNCHRONOUS CONVERTERS : DISCUSSION.

599

may be very disturbing to the magnetic circuit unless protected
in this way.

These fluctuations do not entirely depend on armature reaction, for
as shown by Fig. 20 they are obtained in the exploring coils when no
current is passing in the armature. That is to say, they exist by reason
of the variation of the reluctance of the air-gaps due to the armatures
running slightly out of truth. It is not possible in either case to
observe any side movement, nevertheless, both armatures must be
slightly eccentric in the gap or the shafts bent. A quadruple harmonic
would be caused by a bent shaft or by the armature " whirling." The
fact that the effect is greatest when the field is strongest confirms
this view.

In Fig. 20 the current required to drive the oscillograph (about
^ ampere) was being taken from

SCOTT & MOUNTAIN jr,rLr, cu^Jf^ffn

3 2 AAT^DffS

the slip-rings. To eliminate the
effect of this the first machine
was used to give current for the
oscillograph motor only, at the
same time connecting one strip
to the exploring coil on the .
second machine, which was
belt driven, and entirely dis-
connected from the first. The
curves remained the same
shape but were slightly smaller.
It was not possible to draw or
photograph them by reason of
their slow procession across
the screen.

With regard to Table VIII.
the armature losses are calcu-
lated from the continuous cur-
rent having regard to the
irregular distribution of current
in the conductors. The energy
taken into or supplied by the
armature is a function of both
voltage and current, the energy

flux entering the conductors from the surrounding medium at right angles.
One may thus follow the transfer of energy from the source of supply
to the eddies in the iron through the magnetic flux acting as an elastic
intermediary, and see it dissipated there without the armature current
showing all that is going on, though there will be inevitably either a
rise in current or drop in voltage whenever the effect is taking place.
To obtain a general expression for the losses covering both voltage and
current changes, is, I think, impracticable, but by reference to Table
VI., curves 30 to 32, it will be seen that whenever there is a great
difference between the observed and calculated losses it is accompanied
by a large drop in voltage.

In reply to Mr. Ralph's question the effect is, I think, as follows : —

13!)9l3ll

Dr.
Thornton.

3 8 AMKffes

HOLMES

Fig.

600

THORNTON: SYNCHRONOUS CONVERTERS. [Newcastle,

Dr.

Thornton.

There was first an alternating armature reaction superposed on the
constant excitation. This field was weak, and when the armature was
strengthening the field the permeability of the core would certainly be
less than when acting against the field magnets. The alternating voltage
induced in the field windings depends on how this permeability varies.
If it is simply harmonic no rise in voltage can, I think, occur across the
exciter terminals, but if it varies (as, for example, in the large wave of

R/se of
voUkSigeon
TerminaLs,

EMEon fiebd CermimLs
due Co armdiUfre redLCtion.

EjcdCer voLCcLge,

curve I Plate I. in the paper) with a pointed top to the wave, that is the
point where the voltage will be greatest, for there the permeability is
changing most rapidly. In this case the induced voltage in the field
windings will be greater above the line of exciter voltage than below
and there will be a rise of voltage at the terminals, though the exciter
voltage remains constant. The instrument must have been capable of
reading both alternating and continuous voltage.

I wish to thank several senior students who have helped me in
this work.

1902.] PIGG: RAILWAY BLOCK SIGNALLING. 601

NEWCASTLE LOCAL SECTION.

RAILWAY BLOCK SIGNALLING. V^

By J. PiGG, Associate Member.
{Paper read at Meeting of Section ^ December 15, 1902.)

The subject of signalling generally is of the most interesting
character possible, and code signalling of some form or other seems
to have been in use for the conveyance of intelligence to points beyond
the scope of man's vocal organs during all periods covered by history.
If time permitted we might commence with a quotation from Exodus,
and pass on by easy stages to the methods of signalling of ancient
Egypt, the heliograph of Alexander the Great,* the torchlight signalling
of the Romans, the adaptation of the Greek clepsydra to alphabetical
signalling, the drum, smoke, and fire signals of savage peoples, the
later beacons and watch-towers of our own and other countries,
the revival of torchlight signalling between the Scottish mainland
and the Shetland Isles by the Rev. James Bremner early in the
eighteenth century, and so to the achievements of the brothers Chappe
on the Continent with semaphore signalling, and Lord Murray's
shutter form of telegraph in this country in the period immediately
preceding the introduction of the electric telegraph. It is interesting
to remember that although accounts of the introduction of the electric
telegraph now read like ancient history, yet we are still comparatively
near to the era of the semaphore telegraph. Although formally adopted
by the French Directory in 1793, Chappe's system was not fully
completed in Russia until 1858, so that there may be some here who,
without being of a patriarchal age, and probably taking but little
interest in the subject at the time, may still be said to be contem-
poraries of the semaphore telelegraph.f

The more particular form of signalling to which this paper refers
has also an historical side, which is of considerable interest to the
student of the evolution of railway signalling. There are, moreover,
other aspects of the subject which are of great importance. These
are the statistical, involving consideration of reams of figures relating
to the development of the system and its effects ; the constructional,
with its sight-destroying and brain-puzzling diagrams, illustrating the
principles of design and the circumstances to be met ; and the opera-
tive, with its enormous mass of detail for working purposes. All these
p>oints of view, including the historical, are of the greatest importance

• See Presidential Address of Sir Henry Mance to Institution of Electrical
Engineers, January 14. 1897.

t For further information on pre-electric telegraphs see a most interesting
lecture by Mr. Alderman W. H. Bailey (now Sir W. H. Bailey) at Salford in
1883, "Telegraphs of the Ancients."

602 PIGG: RAILWAY BLOCK SIGNALLING. [Newcastle.

in their several ways, but they require more time to even skim them
lightly than is available here.

There is, however, still another aspect of the subject which, to the
writer, seems to be of supreme importance — the effectiveness of the
system — or, in other words, its adequacy for the purpose for which it
has been designed. However interesting other aspects may be, there
are none of such importance as this. Freedom from failure— and the
consequences — is the touchstone of any system. When, as in railway
signalling, the consequences may be serious, the necessity for reliability
is greatly increased. We might illustrate this aspect of the subject by
quoting figures to show that travelling by railway is vastly safer than
by the old stage coach, the newer motor-car, or even, in view of recent
lamentable occurrences, the electric tram, inasmuch that a smaller
proportion of travellers are killed or injured by the former than by
any of the latter methods. It is the present proud boast of English
railways that they have not killed a single passenger through an
accident to the train in twelve months, and such a record, considering
the millions carried, is a magnificent testimony to the care and atten-
tion devoted by those responsible for the organisation, direction, and
operation of the enormous traffic carried on our railways. Yet
accidents do unfortunately occur, and, if I may so put it, it is small
comfort to the sufferer to know that he is only a unit in a small
percentage of fatalities, and should be glad that the percentage is not
larger.

Objects of Block System.

There is no need on this occasion to labour the point of what is
meant by the term "block." Quoting from the explanation given
with the standard rules, we find that "the object of the system of
block telegraph signalling is to prevent more than one train being in
the section between two block signal-cabins on the same line at the
same time," or from the Board of Trade " Requirements in regard to
the Opening of Railways " : " The requisite apparatus for providing
by means of a block telegraph system an adequate interval of space
between ifollowing trains, and, in the case of junctions, between con-
verging or crossing trains." These extracts, by the use of the word
"telegraph," seem to Hmit the term "block" to the electrical
signalling apparatus, and ignore the outdoor mechanical signals as
part of the " block system." Definitions of the system which may be
deduced from these quotations seem to the writer to be narrow, and
inadequately indicate the functions of the two main classes of apparatus
used for the regulation and control of traffic. Certainly it is impos-
sible to consider either class alone in connection with the results to be
obtained. However, one of tens obtains a more vivid idea of a com-
paratively unfamiliar subject by the use of a simile, and the following
quotation from a popularly- written article in the Pall Mall Gazette
has at least the merit of being graphic, if incorrect : " The world-
famous block system, which, to furnish a simple parallel, decrees that
no train may leave the bottom of a flight of stairs until both tl^^ letter
and the landing beyond have been guaranteed clear,"

1902.] PIGG: RAILWAY BLOCK SIGNALLING. 603

The fundamental basis of block signalling is, therefore, the preser-
vation of "an adequate interval of space" between trains, whether
** following," " converging," or " crossing " ; the object is safety ; and
by convention or rule or regulation it is provided that not more
than one train shall occupy one pair of rails of a certain portion of the
line at one and the same time. For signalling purposes the line is
divided into discontinuous sections, or blocks, and cabins are erected
at suitable points in which, as required by the Board of Trade, the
means of actuation of all points and signals connected with the
running lines are assembled, and in which is also placed the electrical
signalling apparatus. The block section for the time being is the
distance between the two cabins in electrical communication with
each other at the time. These two cabins may not be the two nearest
to each other ; under certain circumstances intermediate cabins may
be switched out and become inoperative for a time. Ordinarily the
space limit between trains is the length of the block section, and it is
never less than this ; but where the distance is 400 yards or less the
space limit may be two or three such sections. It is not necessary
that the space limit be the same at all parts of the line, and, as a
matter of fact, no attempt is made to obtain uniform distance between
trains. At some places it may be only a few hundred yards, and at
others, again, it may be several miles. Nor is it necessary that the
space limits withm any given portion of line should be constant. In
many cases, as already alluded to, means are provided by which, for
economical reasons, the sections and space limits may be purposely
varied. In every case, however, the minimum distance to be observed
depends upon traffic considerations, with which we are not concerned
here, and upon the distance in which the heaviest and fastest trains
can be brought to a stand on the gradients obtaining. In some cases
where there are heavy gradients wc may find that whilst the block
sections are the same for the up and down lines, the space interval is
greater for the line with the falling than for that with the rising gradient.

Main Divisions of Apparatus.

A cursory examination of the subject shows that the apparatus
employed in railway signalling may conveniently be divided into two
great classes — the outdoor mechanical signals, and the electrical signal-
ling apparatus. The former are used for the actual control and
regulation of the movement of traffic ; the latter is provided for per-
fecting the arrangements for the exhibition of the proper signals for
the time being, and is, therefore, an auxiliary. The whole art of
railway signalling, therefore, consists in the exhibition of suitable signals
to the controllers of trains as they approach the sections or blocks.

The forms of the mechanical signals in use in this country are well
known, but there are one or two details respecting them which may
be touched upon here. A certain class of signal, the " distant," may
be passed when in the " on " position. Its indication is of a cautionary
character only when in the position named, and shows that the section
ahead has not been prepared for the free passage of the train, and that

604 PIGG: RAILWAY BLOCK SIGNALLING. [Newcastle,

the driver must be prepared to stop at the next signal in order, the
" home." Drivers, however, are by rule required to be prepared
to stop at any obstruction that may be fotmd to exist between the
" distant " and the " home." Naturally, the positions of " distant "
signals must be at such distances from the "home" signals as to
allow any train to be brought to a stand at the latter if necessary, and
the location of the " distant " is also always made with a view to a
clear sight of it being obtained as early as possible before it is actually
reached. Other signals than the ** distant " are " stop " signals, which
must not be passed by trains when in the "on" position, unless
special permission is given. Such permission may be given by
** calling-on " signals which have a cautionary character when in the
" ofif " position ; or by lamp, flag, or hand signals, supplemented in
some cases by verbal and in other cases by written instructions.
* Home," " starting," and " advance " signals arc all ** stop " signals, as
are also siding and cross-over road signals.

" Stop " signals have other characteristics than those already referred
to. Thus besides being indicators of the conditions existing with
reference to the continuance of the journey, they are also position
signals in that they mark the points which must not be passed by any
portion of a train when the signals are in the " on " position without
special permission. They, therefore, are used to protect the fouling
points. At junctions the "home" signals — and the "distants" where
more than one are provided — are also route indicators for the divergent
lines, since each such line is provided with a separate " home *' signal.
These signals are erected under the same rule for all places, and the
recognition of the road prepared, by drivers, is thereby facilitated.

Interlockjng of Points and Signals.

The means of actuation of all signals have to be interlocked with
each other, and with the means of actuation of the points, so that the
latter must be set before the signals for them are lowered ; so that
conflicting signals cannot be lowered at the same time ; so that points
cannot be moved when the signals are in the " off " position ; and the
points must, as far as possible, be interlocked amongst themselves so
that risk of collision is avoided. Cabins must be so situated as to
provide the best possible view of the line, and to enable the signalman
to see the arms and lights of the signals and the working of the
points. Where signal arms and lights cannot be seen they are to be
repeated in the cabin. Facing points must be avoided as far as
possible, and must not be more than 200 yards from the cabin, and
trailing points not more than 300 yards. All facing points are to be
fitted with facing-point locks and locking bars, and with means for
detecting failure in the connection between the signal cabin and the
points. The length of the locking bars must exceed the greatest wheel
base between any two pairs of wheels of vehicles in use on the line, and
stock rails are to be tied to gauge by iron or steel ties. All points,
whether facing or trailing, arc to be fitted with double connecting rods,
and must be worked or bolted by rods and not by wires.

1902.] PIGG: RAILWAY BLOCK SIGNALLING. 606

These conditions all make for safety, and on their stringency it is
unnecessary to comment here. It is impossible to over-estimate the
importance of the interlocking of points and signals at important
junctions or busy centres of distribution. Such places as busy
passenger station 5rards, whilst they can be, and are, worked without
the ordinary electrical portion of the block system, could not possibly
be worked without interlocking at anything like their present efficiency,
or with the freedom from accident that obtains at present. The inter-
locking in busy yards not only exists between the dififerent levers in
any one cabin, but there is, necessarily, also a large amount of inter-
cabin K:ontrol where a yard is worked by a number of cabins. How
intricate is the control which must be established will be readily seen
from an inspection of the signalling plan of any large station yard.

Power Signalling.

We have, hitherto, considered the working of points and signals
exclusively from the point of view of manual operation. The tendency
to the use of power, under manual control, for this purpose is at the
present moment becoming very marked. The working of points and
signals by electrical power has, of course, been in operation at Earl's
Court Station on the Timmis system for some time. The Great
Eastern Railway Company has put down an installation of the
Westinghouse electro-pneumatic signalling system at Bishopsgate,
and the North-Eastern Railway has recently fitted up two cabins at
Tyne Dock with the same system. The London and North- Western
Railway Company has put down a large installation at Crewe, where
all the necessary operations are carried out by electrical power. This
system, commonly known as the " Crewe " system, is to be put down
at an important junction on the North-Eastern Railway at York.
Messrs. Siemens and Halske also have a very complete system of
electrical piower signaUing, installations of which have been put down
at various places on the Continent. It is impossible within the limits
of a paper like this to enter into details of any system, or even to
consider their advantages. The tendency to the use of power for the
purposes alluded to, in preference to hand labour, is merely noted as a
development which is just in its first stage. Nethertheless, it may be
considered as certain that the subject has received careful attention
from railway engineers, and that such installations would not be put
down, even as experiments, unless there was a fair prospect of their
being successful in promoting either efficiency or economy.

Electrical Equipment and Operation.

Turning, now, to the electrical equipment for the signalling of a
railway, we find a large number of matters of great importance which
the time available will not allow of discussing. Such points are the
signalling of single lines, and the particular conditions to be complied
with; the use of permissive systems of signalling, with recording
instruments for certain classes of line ; the employment of the
telegraph and the telephone as auxiliaries in train signalling ; gate-

606 PIGG: RAILWAY BLOCK SIGNALLING. [NewcasUe,

crossing equipments ; the repeating of signals, lights, points, etc. ; the
apparatus used to indicate when trains or vehicles are standing at a
signal which is out of sight of the signalman, or where the line is not
clearly visible ; rail treadles or insulated rails and their uses, or other
special devices which go to make a complete system. We have not
even time for an analysis of the codes and regulations under which
signalling is carried on ; for a discussion of the relative merits of three-
wire or one-wire systems; or for the much-debated question of the
best form of instrument, from either the electrical point of view or from
the operator's standpoint. The latter question is quite as easy of settle-
ment as the question of the best arc lamp or the best motor, municipal
versus private trading, provision for the depreciation of plant, or any of
the numberless matters on which many people agree to differ more or
less amicably.

The electrical equipment for a block section is very simple, but the
amount of apparatus to be provided at any block station depends upon
the character and importance of the place. If we take the simplest
example of such a station, say a mere passing place, we shall find that
where single-needle apparatus is employed the equipment will consist
of two bells and four such instruments. One bell and two instruments
will be in electrical communication with the block station on the up
side of the cabin considered, and the remainder in connection with the
cabin on the down side. The bells are for the purpose of giving and
receiving information, or for the making of arrangements in accordance
with the voluminous code which provides for all circumstances
that may arise in connection with the working of traffic. The instru-
ments are also used to a slight extent in connection with the code, but
they have other and more important duties to perform, in that they are
intended to indicate continuously the condition of the lines of rail
they represent.* There are numerous forms of block instrument in use,
each embodying, no doubt, its designer's idea of the best method of
performing the desired operations, but with constructional details we
are not at present concerned, and so far as their indications are con-
cerned they are all alike in that they represent the condition of the line
by convention only.

A study of the code and regulations for the working of traffic shows
that there arc three conditions of the line which the block instrument
should indicate. These are :

"Line Blocked," "Line Clear," and "Train on Line."
The first is the indication to be given when the section is clear of trains
altogether ; the second is the indication required when the section has
been prepared for a train, but which has not yet entered the section ;
the third is the indication provided to show that a train is actually
passing between the two block stations. Each of these indications is
" permanent," in the sense that it is required to be exhibited during
the whole time the condition it represents continues ; the indications
on the two instruments representing a line of rails, in the two cabins,

• On the N.E.R. the use of the indicators in conneclion with the code has
been discontinued since the paper was read.

1902.] PIGG: RAILWAY BLOCK SIGNALLING. 607

are the same, and the indications are under the control of and made by
the man towards whom the train signalled is proceeding — i.e., at the
exit of the section.

The operations necessary to the passage of a train may be briefly
described, it being premised that the character of the train is immaterial
for the present purpose. Suppose a train is approaching station " C *'
on the up line and will pass on to " D." Station " C askes station " D"
by code " Is line clear ? " (there are 1 1 variants of this signal). If the
train may proceed, " D " replies by code to that efifect, and gives an
indication on the block instrument for the up line at his own station and
at " C,** which reads " Line clear." This indication remains until a
further stage of the operations, and serves as a continual reminder to
" D " that he has given permission for a train to leave " C," and to the
signalman at the latter station it serves as a continuous reminder that
he has obtained permission to forward a train. Under the conditions
now obtaining the signalman at " C " may place his mechanical signals
in the " off " positions to allow the train to proceed to " D."

When the train is leaving " C " the signalman there sends the " Train
entering section " bell signal to " D," who must acknowledge it and
change the position of the block indicators in his own and "C's " cabin
for that line to " Train on line," and this indication serves as a con-
tinuous reminder to both signalmen that there is a train in the section.
When the train has passed " D " and gone forward under precisely
similar conditions, the signalman there advises '* C " that the section is
again clear by giving the *' Train out of section " dial signal, and leaves
the needle of the block instrument in the " Line blocked " position. In
the diagram the various conditions may easily be followed.

Relative Responsibility of Signalmen.

If we consider the functions of the two signalmen, we find that for
traffic in one direction one of them is more responsible than the other.
The signalman at the exit is the person who gives permission for a train
to "enter the section, and before doing so he must assure himself that

608 PIGG : RAILWAY BLOCK SIGNALLING. [Newcastle,

the conditions obtaining are suitable. Further, he must arrange for its
disposal on arrival at his cabin, and see that it is in such condition as
will justify him in clearing the section after it has passed out. The
signalman at the entrance to the section cannot, under normal circum-
stances, authorise a train to proceed without having obtained the permis-
sion given by the acknowledgment of the " Is line clear ? " signal, and
the giving of the " Line clear " indication. Hence the responsibility
for the authorised progress of the train rests with the signalman towards
whom the train is proceeding. The signalman at the entrance becomes
the guardian of the section, and must protect against the entrance of a
train by the exhibition of the proper signals. For ordinary double-line
working one signalman is, of course, the sender for, say, the up line and
the receiver for the down line, so that responsibility is averaged for the
total traffic.

If we carefully consider the relationship existing between the two
divisions of apparatus, we find, as already stated, that the electrical is
an auxiliary to the mechanically-operated outdoor signals, and exists
for the purpose of perfecting arrangements for the safe dispatch of
traffic between persons charged with its control, situated at considerable
distances apart, for the purpose of indicating the condition of the line
between those persons at all times, according to fixed conventions or
rules, and for the notification of its passage from point to point. The
safety of the system consists in the actions of all parties to the movement
of trafi&c being synchronised, and as this most important point is only
possible by the aid of the electrical equipment, its value as an adjunct is
extremely great.

If we look over the requirements of the Board of Trade with
reference to the electrical portion of the signalling apparatus, we are at
once struck with their meagre character as compared with the require-
ments for interlocking. The first requirement reads : " The requisite
apparatus for providing, by means of the block telegraph system, an
adequate interval of space between following trains, and in the case of
junctions between converging or crossing trains." Then, curiously
enough, under the head of " Interlocking," we have : " The signal cabin
to be commodious, and to be supplied with a clock and with a separate
block instrument for signalling trains on each line of rails."

If we contrast the wording of the requirements with reference to
the operation of the two classes of apparatus, we cannot fail to observe
the great difference in the degree of precision in the language employed.
Referring to the requirements with regard to interlocking, we find that
the signalman " shall be unable " to lower a signal until after the points
are set for the road controlled by that signal ; that " it shall not be
possible " for him to exhibit signals which will give rise to a collision ;
and that " he shall not be able " to move points connected with a line
the signals for which have been previously lowered. There is no
similar precision in the requirements for the electrical apparatus, the
references being as already quoted : " The requisite apparatus . . . " ;
" a separate block instrument for signalling trains on each line of rails."
Turning to the standard code, we find the general regulation to read :
" All fixed signals must be kept at danger except when it is necessary

1902.] PIGG: RAILWAY BLOCK SIGNALLING. 609

to lower them for a train to pass ; and before any signal is lowered,
care must be taken to ascertain that the line is clear, and that the block
telegraph and other regulations have been duly complied with."

Limitations of Ordinary Systems.

If we consider the limitations of such a system of signalling as has
been outlined, we find that its greatest weakness arises from the want
of interdependence between the two divisions of apparatus. Theo-
retically, the arrangements are perfect ; one signalman acts as a check
upon the other in so far as they are both concerned in any operation,
and the interlocking checks inadvertent error in the operation of the
outdoor signals at either block station in so far as fouling routes are
concerned. But neither signalman has a complete check on the actions
of the other, and as the operation of the mechanical signals is in no
way dependent upon the block instruments, the operations need not
necessarily synchronise, and interlocking will not prevent following
collision where operations of the signals may be repeated without
check. The sending signalman depends upon the observation of the
man at the exit of the section when the latter accepts the " Is line
clear ?" signal, and must necessarily do so; the receiving signalman
relies upon the man at the entrance to the section not to send trains
into the section without the usual acceptance and subsequent notice of
the change of position of the train, but is powerless to control his
actions ; and both signalmen rely upon the due observance by the
drivers of trains of the signals exhibited for their guidance. Hence
there are three independent persons engaged in the movement and
control of traffic, any one of whom by a dereliction from duty may be
the cause of accident. Accid ents caused by deviations from the regula
tions provided for their guidance have occurred frequently in each of
the three conditions referred to, and a study of the Board of Trade
inspectors' reports show that by far the greater majority of accidents to
trains occur through the failure of one or other of the persons named to
carry out his duties in the manner prescribed. Such failures are due,
of course, to those temporary aberrations which, for want of more
knowledge, we call absence of mind, but which seem inseparable from
human existence. Carelessness, in the sense of deviation from regula-
tions, there may be, but it should not be forgotten that men necessarily
have other interests, other causes for thought, and that those most capable
of concentrating their attention are always more or less conscious of
other thoughts obtruding on their notice.

The object in contrasting the Board of Trade requirements with
regard to interlocking with the less onerous stipulations for the
electrical apparatus, is not to suggest that simifar requirements should
be imposed with regard to the latter. As a matter of fact, the railway
companies have, generally speaking, been much in advance of their
obligations, as will be seen when it is stated that, whilst the Act of
Parliament making the block compulsory is dated 1889, and the require-
ments of the Board of Trade with reference to the Act are dated 1892,
the decade during which the greatest progress was made in installing

610 PIGG: RAILWAY BLOCK SIGNALLING. [Newcastle,

the block was that of the seventies. Railway companies have spent
enormous sums in equipping their lines with signalling apparatus,
which, from the operating point of view, works well on the whole, and
which, by the high degree of certainty that it introduces, has also con-
tributed largely to speedy transit. Naturally, before scrapping their
present apparatus and incurring the enormous expense which such a
course would involve, they desire to assure themselves that any
suggested change of procedure will have the advantages claimed for it.
A well-known American signalling engineer some time ago said that
absolute safety could only be assured by building a track for each train
operated. The most rabid perfectionist would hardly desire to push
his requirements so far as absolute safety if it is to be obtained at such
a cost. Perhaps the American gentleman only desired to indicate that
" absolute " perfection is unattainable.

Lock and Block.

The system of signalling considered is the manually operated and
manually controlled, and its limitations have been referred to at some
length. We may now briefly consider what suggestions are available
for reducing the risks which experience shows have to be run from
failure of the controllers. Generally, such systems are known by the
not very appropriate or self-descriptive name of " lock and block," and
they have as their object the union of the mechanical signals with the
block apparatus, so as to make their operation interdependent, as far as
consideration of the conditions obtaining may seem desirable. In this
country systems have been devised, among others, by Sykes, Spagnoletti,
Langdon, Saxby and Farmer, Tyer, Evans, and O'Donnell. Such
systems, however, form at present but a very small fraction of the
signalling apparatus in this country.

We have seen that the signalman at the entrance to a section may,
with the ordinary system, send a train away without the concurrence
or even the knowledge of the signalman at the exit. In order to pre-
vent this, the signal controlling the entrance to a section is so inter-
locked with the block instrument at that end that it cannot be lowered
to admit a train unless the man at the exit has given *' Line clear," and
so accepted responsibility. We know also that after sending a train
away the signalman at the entrance may neglect to replace his signals
to danger, and so, under certain circumstances, admit a following train.
To prevent this, a complete lock-and-block system provides that a train,
after passing the signal controlling entrance to the section, shall
automatically put that signal to danger, and so protect itself if the
signalman neglects to do so. Replacement of the signal lever in the
normal position for dzyjger results in it being locked by the block
instrument, which prevents it being used again until another " Line
clear " signal is given from the exit. We have also noted the fact that,
with the ordinary system, the signalman at the exit can give " Train
out of section" for one train and " Line clear" for one following, quite
irrespective of the actual condition of the section, and before the first
train is out. To remedy this the instrument controlling the indications
at both cabins is arranged to lock itself by the operation necessary to

1902.] PIGG: RAILWAY BLOCK SIGNALLING. 611

give " Line clear." This lock is maintained until the train so signalled
has passed the signal controlling entrance to the next section, or has
otherwise been disposed of. Hence we see that the operations of the
signalman are cyclic, and are intended to be made in a given
order. Further, we see that the operations of the signalman are
checked on the points where risks of error exist in the uncontrolled
^sterns.

Whilst the union of the signals and block instruments compels,
under ordinary circumstances, cyclic operation by the signalmen, it by
no means follows that the movements of all classes of traffic is, or can
be, made in one unvarying order. Circumstances are constantly arisin*g
which necessitate deviation from the simpler routine of a block section,
and means have to be provided to meet them. These are obtained by
the provision of a " releasing key," by the use of which certain parts of
the cycle necessary under ordinary conditions may be anticipated or
dispensed with. The importance attached to the use of the release key
may be gauged from the rules relating to its use for "cancelling,"
" obstruction danger," and " blocking back " signals, failure of rail
contact, etc., and the special caution to signalmen " not to resort to the
key until they are quite satisfied that its use is really necessary."
Practically speaking, the provision of the releasing key is an acknow-
ledgment of the want of sufficient flexibility to meet such cases as
occur in the common operations necessary to the movement of traffic.
As such, it is also an infraction of the automatic character of the
system^ and again saddles the signalman with the responsibility, under
the ordinary system, of which it is the object of the lock and block to
relieve him. Granted that the automatic character of any apparatus
may be infringed for a legitimate purpose, and it ceases to be automatic.
If use can be made of such apparatus under conditions that are suitable,
there is nothing to prevent its use under misapprehension. If a mis-
apprehension exists with reference to the conditions, no large-lettered
cautions will prevent its use, as the signalman will be satisfied of its
necessity, and recording use of the key in the train-book will not avert
the consequences of the act. Instances have occurred where use of
the release key under misapprehension has had serious results. Hence,
whilst the lock-and-block is undoubtedly a step in advance of the
ordinary system, it cannot be regarded as infallible, since in the use of
apparatus provided to meet certain contingencies the signalman must
exercise his judgmem as to whether the circumstances absolutely
warrant the course.

The type of rail treadle used in lock-and-block systems has the
grave defect that it will clear a section behind it when under certain
circumstances the line may not be clear. Such treadles are actuated to
perform the release operation at the starting signal by the iirst vehicle
passing over them, and so may clear a section by the first portion of a
train which has become divided. Hence, although the block instru-
ment would be released by the first portion of a train, and may again
be used immediately, yet the signalman must personally assure himself
that the whpl? tr^iQ has passed, as he has to do in non-automatic
systems.

612 PIGG: RAILWAY BLOCK SIGNALLING. [Newcastle.

In connection with the safety of snch a system, we have with
certain classes of instruments further to consider the effects that may
be produced by contact between the block wire of either instrument
and another working wire, and of the effects of atmospheric discharges.
It is not the custom to build separate telegraph lines for the block
circuits any more than it is not the custom to provide a separate track
for each train operated. Line contacts, no doubt, still occur occasionally,
and lightning protectors do not always protect.

Fog Signalling, etc.

It will be noted that the lock and block does not provide checks to
obviate the consequences of neglect or inadvertence on the part of one
of the persons concerned in the movement of traffic — the driver. He
is left altogether out of consideration, and must rely upon himself for
due observance of the signals exhibited for his guidance. Yet the
driver is probably the most important of the persons concerned, since
he is the actual controller of the means of movement of traffic, and
is the last link in the chain of checks imposed by signalling systems.
Whilst accidents have taken place from disregard of signals in clear
weather, the duties of drivers are most onerous during fogs or snow-
storms, which obscure the sight of the signals by which they are guided.
Under such circumstances the visual signals are supplemented by
explosive signals directly operated by the passage of trains over them.
The detonators, which are placed on the rails in the neighbourhood of
the signals by hand, by men specially collected for the purpose when
such signalling becomes necessary, are the danger signals, but they are
supplemented by signals with hand lamps, for which the drivers and
firemen must watch. The signals themselves are operated by the
signalmen in the usual way, and the fog-signalmen act in accordance
with the positions of the signals from time to time. Whilst a signal is
at danger the detonators must remain on the rails ; when the signal is
off they are removed. The off position of a signal which cannot be
seen is therefore indicated to a driver by the absence of an explosion,
and the hand-lamp signals.

Such a system is most expensive to the companies, entails consider-
able exposure and hardship upon the fog-signalmen, and suffers from
defects of a practical character in operation. The collection of the
men for fog signalling occupies some time, as they have to be with-
drawn from other duties, or to be brought from their homes. The
person who has to decide upon the necessity or otherwise of com-
mencing fog signalling is not the person most vitally concerned, or
who has effective control of the movement of the traffic affected. Fogs
are sometimes of a deceptive character, and appear differently to a man
on the foot-plate and another on the ground, and they change in
intensity very rapidly on occasion. The " All right " signal is partly
of a negative character, in that it is given by the absence of explosion,
together with the hand-lamp signals. The latter signals may or may
not be seen by a driver or fireman. Sight of such signals involves
either continual concentration for the purpose, or the ability to localise
positions so as to be able to look specially for th^m at the proper time.

1902.] PIGG: RAILWAY BLOCK SIGNALLING. 613

This question of localisation of position is of some importance.
Experienced drivers, of course, know the " feel " of the road perfectly
well, and localise their position from a large number of local circum-
stances, such as the passing of (over and under) bridges, curves,
cuttings, signals, cabins, stations, etc., all of which "talk" to them.
Whilst this is the case at ordinary speed the indications are not so
plain at lower speeds, and, moreover, approximately the same indica-
tions may be met with at different parts of a journey. Hence, taking
all things into consideration, the present system of fog signalling leaves
something to be desired.

Attempts have been made to place the operation of the fog signals
in the hands of the signalmen, but whilst such methods enable the
system to be brought into use more promptly than when hand signal-
ling is resorted to, and obviate hardship and exposure to the fogmen,
it does not alter the character of the signal, and, moreover, it does not
allow of personal supervision, and abolishes the supplementary hand
signals. Probably the most promising systems for superseding the
ordinary fog signalling are those which provide for the signal being
given directly upon the engine itself, and for it to be in constant
operation. There is quite a large number of such systems available
now, but taking the whole country into consideration their adoption is
not proceeding at a great rate. Some of the systems referred to are
mechanical, such as that devised by Mr. Raven, of the North- Eastern
Railway, and which is being fitted to a large number of the company's
engines ; others are partly mechanical and partly electrical, as Mr.
Brierle/s system, which has been introduced by Messrs. Saxby and
Farmer; others again are wholly electrical, such as the method of
signalling devised by Lieutenant-Colonel Bolitho. The majority of
such systems operate by means of an obstruction working in conjunc-
tion with the signal to be indicated, placed on the line, which gives an
alarm on the engine, and so calls attention to the position of the signal.
In Mr. Raven's system the alarm is a special whistle which may be
operated by steam or compressed air. In Mr. Brierley's and Lieutenant-
Colonel Bolitho's systems attention is drawn by means of electric bells
and discs, and electric bells, respectively, carried on the engine. In
the latter the electrical circuits are closed by contact with steel brushes
placed on the line side in a similar way to that previously used by Mr.
Burns and others. In some of the systems an alarm when the signal is
'* on *' is considered sufficient ; in others, again, provision is made for
repeating both the "on" and "off" positions, so that the signal is
positive in both cases.

It is, of course, impossible to enter into a detailed description of
such systems, or even to enumerate all of them. Mention, however,
should be made of the system devised by Mr. W. S. Boult, in which
necessity for contact between parts of moving vehicles and obstructions
on the line is obviated. This is done by the use of permanent and
electro magnets placed on the line, the latter being operated in con-
junction with the signals. The magnets act upon polarised relays
carried upon the engine in such positions as to pass immediately over
the former, and the relays operate appropriate circuits for the purposes

614 PIGG: RAILWAY BLOCK SIGNALLING. [Newcastle.

required on the engine. The indications given on the engine are visual
(miniature distant and stop signals, and numbered and coloured discs)
and aural (bells). The system distinguishes between " on " and " off/'
between "distant" and "stop" signals, provides route indicators to
show on the engine which road has been prepared at junctions, is
capable of repeating the signals in the cabins, and is self-testing for
both engine and line circuits. Failure of the line or engine circuits
also results in the danger signal being given at the next signal
approached after the failure, and partial failure of the latter circuits
is distinguishable. One special feature of the system lies in the fact
that the last indication received on the engine remains until the next
signal is reached, and so serves as a continual reminder of the condi-
tions under which the train is running. This result is not obtained
with the present system of visual signalling, and its value in a case
where a driver has failed to comply with the signals exhibited is
obvious, whilst the ability to distinguish between distant and stop
signals is a valuable characteristic for purposes of localisation. The
indications given upon the engine are of the most positive character,
the semaphore arms being first thrown to " danger," after which they
either remain in that position if the actual signal is "on," or are
immediately lowered if the signal is "off." The system is of the
most complete character, and its design shows the closest study of the
conditions to be met, whilst the details of the apparatus are most
ingenious and at the same time very simple. Its adoption would
revolutionise the method of signalling, since practically there would be
no necessity for providing the mechanical signals now in use.

The selection of a system of auxiliary signalling such as has been
considered has a business aspect, as well as the technical and
operative sides. In order to get the utmost value from such a
system, it should, since engines run over other companies* lines than
their own, be uniform for all lines if possible, or at least for the
lines over which interchange of locomotives takes place. Some com-
panies might be able and willing to pay more for the additional
security to be obtained than others ; and some, again, might consider
certain precautions essential which to others might appear to be
superfluous, or not worth the cost of obtaining. The matter is one
for common agreement amongst the companies running over each
other's lines. Otherwise, the subject is likely to prove a worthy
successor to the position so long held by proposals to supersede the
cord communication by electrical means — a matter for wordy debate
to be settled eventually by the adoption of other means.

" Automatic " Signalling.
Summing up the situation as it appeared to him in 1898, the present
speaker wrote : " Railway signalling appears to have now reached a
stage at which some departure from the present methods seems
probable. The lines upon which changes will be made will, in all
probability, result in a greater degree of automatic control than
obtains at present." The indications at present seem to confirm this
view very strongly, and we appear to be likely to see early changes in

1902.] PIGG: RAILWAY BLOCK SIGNALLING. 615

the methods of signalling of the most radical character. The American
" track circuit " system is gaining a footing in this country, and if it
should be found suitable for a country where junctions are so numerous
and near together, and where the great bulk of traffic is between points
comparatively near to each other, a revolution will be effected which
will at once change the whole character of signalling in this country.
And there is no more reason to doubt that the success of such a system
will result in financial relief to the companies than there is to doubt the
necessity for such relief.

In this country there is already an installation of automatic signal-
ling in operation between Grateley and Andover, on the London and
South-Western Railway, in which the signals are actuated by air on
the low-pressure system, the movements being controlled by the
positions of trains on the line, which is formed into track circuits.
The North-Eastern Railway Company has also made arrangements
with the Hall Signal Company of America to equip a portion of their
main line to the North, between Alne and Thirsk, with a track circuit
system of automatic operation. This installation will differ from the
ordinary Hall system — in which the signals are operated by electric
motors — and from the London and South-Western Company's installa-
tion, in that the signals will be self-contained as regards motive power.
Movements Will be made by carbonic acid contained in steel cylinders
at a pressure of 600 lb. per square inch, the working pressure being
50 lb. As many as 10,000 movements can be obtained before it
becomes necessary to recharge. At the junctions between Alne and
Thirsk the automatic signals leading to fouling points with the branch
lines will also be under manual control, so as to admit of branch
working. Such cabins, however, will be closed at times when the
branch traffic ceases. The sections will be shorter than ordinary.
Siding points connecting with the main line in the purely automatic
sections will be provided with indicators communicating with several
of the rear sections to show whether trains are approaching before the
switches are opened for the siding. It is expected that a considerable
annual saving in the working expenses for the signalling of that portion
of the line will result from the change, and if this is effected and the
system is otherwise satisfactory, no doubt further extensions will follow
in the near future.

Taken on the whole, railway signalling in the States is of a very
mixed character, and varies from the antiquated "train dispatcher"
system, with or without telegraphic communication, through the tele-
graphic, the manually operated, manually controlled, and the con-
trolled manual, to the automatic systems. There is not time here to
discuss these systems, or the many other interesting details of American
signalling, such as, for instance, the relative advantages of the " normal
clear " or " normal danger '* positions for signals ; two or three p)osition
signalling ; track sections versus treadles for the controlled manual ;
the simple single signal, the overlap, or the home and distant systems ;
the operation of signals by electricity or air, and high or low pressure
for the latter ; track batteries and relays ; the bonding and insulating
of rails ; and other matters of a very practical character. The auto-
VOL. 82. 41

616 PIGG: RAILWAY BLOCK SIGNALLING. fNewcasUc,

matic system seems to have taken firm hold, and when we consider its
advantages as looked at in the States, there seems to be little cause for
wonder that it has done so, especially in a country where long con-
tinuous runs between diverging points are common. The reasoning
adopted is very plain, as the following quotations from a series of
articles in the Electrical Review last year will show : " If the substitu-
tion of automatic devices for the control of a system formerly under
human control and operation (the controlled manual is being referred
to) produced such beneficial results, why, one naturally asks, should
not the introduction of automatic mechanisms for its operation pro-
duce like benefits." " It " — the automatic system — " is constantly on
duty, requires no relief substitute, never goes on strike nor tires of its
job, never sleeps, gets drunk, or deserts its pals, and never misconstrues
orders." " The ideal system is one in which the train in a block has
control of the signals governing the entrance to that block." "The
system affords means of detecting misplaced switches in the block, of
failure of cars on a side track to stand clear of the running line, has
frequently detected broken rails and obstructions in switches, it affords
opportunity for trackmen to protect blocks during emergencies, and
for protection during repairs." "Operators for such a system are
superfluous, and could only be of use in case of derangement." " Rail-
road officials are universally awakening to the possibilities of automatic
signals, and that wages are better utilised in obtaining automatic
operation."

Another advantage claimed for the automatic system is that the
carrying capacity of a line may be increased from the facility with
which the block sections may be shortened. On this subject, how-
ever, the last word is not with the signalling systems, since the lengths
of the sections must always be such as to allow any train, whatever its
speed, weight, and braking power, to be brought to a stand in the space
allotted. The suggestion, moreover, involves a levelling of speeds^
which again will require limitation of loads for mixed traffic, since
the standard of speed will always be set by the fast passenger .traffic.
There is no tendency ascertainable in either of these directions at
present.

Further study of automatic systems shows the great necessity for
supplementary signalling under exceptional circumstances, such as
fog or snow, since there is no personal supervision. Some form of
apparatus giving the signals on the engine would seem to be
imperative.

Where automatic signals are in use, the rule that a stop signal shall
not be passed when in the danger position unless other signals are
given which are recognised as superseding it, must necessarily be
abolished, and a time limit of detention at the signal imposed, after
observance of which the train goes cautiously forward until ordinary
signalling is resumed in the sections ahead. Unless special regulations
or provisions are made, and in the event of prolonged operations at a
point giving access to the main line, this may result in a train arriving
at the signal actually protecting a train drawing on to the main line^
when, of course, the space limit will not be observed.

1902.] PIGG: RAILWAY BLOCK SIGNALLING. 617

In the States, it is usual to distinguish signals which may be passed
at "danger" after a time interval from those which, being under
manual control, may not be passed without special instructions.
Where signals are at one period automatic and at another under
manual control, the conditions are more complex.

Possibilities of Signalling with Electric Traction.

We have seen that the adoption of human control for railway
signalling has necessitated the imposition of numerous checks upon
the actions of the controllers, and has required considerable auxiliary
apparatus for a variety of purposes. The adoption of automatic
signals dispenses with all the costly apparatus referred to, except at
junctions where, owing to the want of selective properties, automatic
systems are unsuitable. The question for consideration now is, " Is
the automatic system, as described, final ? " If we consider the present
outlook with regard to railways, we find that we are probably on
the eve of a very great change in methods and even routine of
transportation. The great question to be now decided concerns the
use of the self-dependent locomotive, or, as an alternative, the use of
locomotives taking their power from their locality, wherever that
may be, in the line of their run. The question is not entirely confined
to steam and electricity, although at present these two are the only
ones worth considering. As all are aware, the railway companies are
taking action in consequence of the incursion of the electric tram into
what has hitherto been practically a monopoly. The directors of the
North-Eastern Railway are considering tenders for the equipment
of part of their lines in this neighbourhood for the use of electric
power; the Lancashire and Yorkshire have partly completed their
arrangements ; the London and North- Western are said to be
considering the question ; and the Great Eastern are to apply for
powers for the same purpose as early as possible. The proposals now
being put forward are for comparatively short-distance suburban
traffic ; the electrification of long-journey main lines is not just
yet.

The point for consideration here, however, is not the suitabilitv or
otherwise of electric traction, but the effects that it may have on
signalling. If we look over the principal equipments of a train, we
find that we have steam for locomotion; gas, oil, or electricity for
lighting ; and pneumatic appliances for braking. Electricity is
capable of displacing all these for each of their several purposes. As
electrical power is delivered to the locomotives from the outside, we
have presented to us conditions which have no precedent, and oppor-
tunities for outside control such as have never before existed. Hitherto
the driver has been the sole actual controller of the means of loco-
motion, and short of throwing the train off the line, or into a dead end,
no other person could affect the results when he neglected certain
duties. With electricity all this is altered, and we have to deal with
an agent which is easily handled, and lends itself readily to automatic
or other control and operation. American automatic signalling gives
contro} 9( the signals to the train requiring their protection. Where

618 PIGG: RAILWAY BLOCK SIGNALLING. [NewcasUc,

supplementary signalling is in use to check error on the part of the
driver, its design is generally with a view to direct action on the
control of the motive power, rather than to call attention to a derelic-
tion of duty, as with us. With electric traction there should be no
difficulty in arranging to give such direct control to the train which
requires to be protected by cutting off the power from all sections that
would endanger its course, whether these are "following," "con-
verging," or "crossing." Signals as now used would then be super-
fluous, except at such places as those where selection of traffic
rendered them necessary. Control of the motive power is a far more
effective check on inadvertence than any other that can be devised.
The whole aim of the signalling now in use on railways is to control
the man who controls the motive power. If we can give to a train the
means of controlling the motive power to other trains, which may be
sources of danger to it, the men who control the motive power on those
trains will no longer count in connection with the subject under notice.
After all, automatic signalling, as described, does no more for the
driver than the manual or the controlled manual, if as much, since it
removes the personal supervision now provided, which is not always
faulty, and has on many occasions been of the highest possible
value.

The author's thanks are due to Mr. Raven, of the locomotive depart-
ment, and Mr. Ellison, the superintendent of the telegraph department
of the North-Eastern Railway, and to Mr. Fletcher of the L. and N.W.
Railway, for the loan of apparatus for use at the meeting.

Hciiviside. Mr. A. W. Heaviside said that, with regard to Mr. Pigg's paper on

" Railway Block Signalling," they were certainly obliged for such an
exhaustive statement of what is done in this direction at the present
time, which is a very critical one in the history of block signalling.
He was one of a party which recently visited Tyne Dock to see the
system in operation there, and it occurred to him that the capital cost
was very considerable— rather more than the ordinary system. He did
not see why they should not do the whole thing electrically, and not
use pneumatic power at all. If a man were to commence to build a
new railway at the present time, he did not think it likely that he would
proceed on the same methods as the existing arrangements. The old
system requires a great deal of maintenance. Mr. Pigg had said that
the North-Eastern Railway Company had employed the telegraph and
the telephone as an auxiliary, and he would be very glad to hear more
about his experiences with the telephone. There were many other
interesting questions which might be raised, but in the absence of Mr.
Pigg it was rather difficult to carry the discussion much further.

Mr. Moir. Mr. A. MoiR said that, while asking for more seemed rather

ungracious, seeing the paper was so long and exhaustive, if Mr. Pigg
had been there he would have liked to have asked him what the
resistance of the block coils is which they use on the North-Eastern
Railway, how many amperes were required to actuate the instru-
ments, what sort of primary battery did they find gave best results ;
also whether secondary cells have been employed with any success

1902.] RAILWAY BLOCK SIGNALLING: DISCUSSION. 619

Mr. R. M. Longman : With reference to Mr. Pigg's statement that Mn
no passengers lost their lives in 190 1, it may be added that many fatal
accidents occurred at highway level crossings, due in many cases to
carelessness or forgetfulness on the part of the gatemen, who often
open their gates without placing their signals against the trains. A
little interlocking device would thus save many lives.

Mr. J. PiGG (in reply, communicated) : I regret that a misunderstanding Mr. Pigg.
and my recovery from an illness led to my absence from the meeting
of January 19th and have further prevented a full discussion of the
problems to be met with in railway signalling. There can be little
doubt, as remarked by Mr. Heaviside, that the capital expenditure for
such a system as he inspected is greater than that for the ordinary
system ; but if a commensurate saving is effected, either in labour or
by facilitating the operation of traffic, the increased expenditure will be
justified. Whether such a saving will be shown remains to be seen.
The period of use is at present too short to enable a reliable opinion to
be formed. It must, moreover, be remembered that the maximum
economy is not to be expected from such a system in small isolated
installations with separate equipments for motive power.

The employment of the telegraph and telephone in connection with
the operation of railway traffic is, as stated, auxiliary to the ordinary
block signalling, and does not differ materially from the methods of
using such instruments elsewhere. They are not used directly in block
signalling, but for perfecting arrangements before traffic is allowed on
the line, or for giving information beyond the scope of the code, or for
communication between block points not directly connected for sig-
nalling purposes. The telegraph is used for transmitting notice of the
times trains leave or pass certain points to other places on their routes,
so that proper arrangements can be made for dealing with them without
unnecessary delay to other traffic. The telephone is used for similar
purposes, but more locally and over less extended distances ; although
valuable auxiliaries for the working of traffic, they are not, of course,
part of the block system proper.

With reference to Mr. Moir's questions, the block indicators in use
on the North- Eastern Railway are wound to a resistance of about
150 ohms. The batteries used are the ordinary porous-pot Leclanche
cells. A six-cell battery is used for the pinning instruments, and a
four-cell set for the non-pinning. (Since the reading of the paper the
North-Eastern Railway has ceased to use the block indicators in con-
nection with the code, and no doubt the non-pin batteries will be
dispensed with.) I have no idea of the minimum current required by
the block indicators. On the North-Eastern Railway they work perfectly
well with ten milliamperes, but they are never intentionally worked with
the minimum.

Secondary cells have not, to the writer's knowledge, been tried
anywhere for block working, and the prospect of their adoption does
not seem very great. The first cost and maintenance of such cells
would seem to be necessarily greater than that of primary cells, and
the amount of apparatus in the average signal cabin hardly calls for the
adoption of the universal battery system which the use of storage cells

620 PIGG: RAILWAY BLOCK SIGNALLING. [Newcastle,

Mr. Pigg. SO greatly facilitates. Moreover, such a battery arrangement is for
railway signalling an operation of the nature of putting too many eggs
in one basket. It is desirable that the signalling of the different lines
should be as independent as the lines themselves are for the operation
of traffic.

There is a certain amount of truth in Mr. Longman's remarks
respecting accidents at gate crossings. Accidents do occasionally
occur at such places, but although the writer has mixed intimately with
gatemen over a considerable area of this country, and although he pays
great attention to the reports of the inspectors of the Board of Trade,
he would not go so far as to say that they often open their gates without
placing their signals against the trains. There are many cases in the
writer's own knowledge where signal cabins are erected at highway
crossings solely on account of the traffic on the road. In these and in
all cases where the gates and signals are worked from one point the
gate- wheel is interlocked with the signal levers. In others cases a
dwarf frame is provided which affords the interlocking referred to.
At gate crossings between block points many companies provide
electrical apparatus, connected in the block circuits passing the gates,
by which the gateman is constantly aware of the condition of the line
on both sides of his gates.

1903.] CHArrOCK; MOTIVE POWER SUPPLY. 621

LEEDS LOCAL SECTION.

MOTIVE POWER SUPPLY FROM CENTRAL
STATIONS.

By R. A. Chattock, Member.

{Paper read at Meeting of Section^ February igth^ ^90J.)

The development of a supply of electric energy for motive power to
private consumers has been occupying the attention of Central Station
Engineers for a considerable time, and, during the last two or three
years, has been stimulated very much by the excellent results that have
been obtained in several large towns. It is obvious that, given a large
network of mains that has been laid for the purpose of supplying light-
ing consumers, it is to the interest of these consumers, as well as of the
authority responsible for the supply, to have as much current as
possible distributed through it, especially during the hours of daylight.
The lighting consumer benefits by the greater output combined with
the increased load-factor at the generating station, making it possible
to generate current at a cheaper rate. The supply authority benefits
by being able to reduce the cost of supply and by having the demand
for current stimulated. The standing charges on the cost of the mains
are spread over a greater output and so reduced proportionately.

Direct-current stations, so far, have done most in developing this
branch of the supply. This is probably because the direct-current
motor has, up to recent times, been more easily applied to existing con-
ditions, and has proved a more reliable and efficient machine than the
single-phase alternating-current motor. Now that alternating-current
stations are changing over to, or putting down, auxiliary, two- and
three-phase plant, this disadvantage should disappear, and the engineer
in charge of such a station should be able to follow in the steps of his
direct-current brother.

It may be interesting to give a short description of what has been
done in connection with a supply of current, for motive power, by the
Corporation of the City of Bradford. The supply is by means of direct-
current, the voltage being 230 or 460. The first motor was connected
to the mains in 1891. There was not much development until 1897,
when the Corporation inaugurated a system of hiring out motors, and at
the same time reduced the price for current to 2id. per unit. In 1896
the percentage of current sold for motive power to the total output was
only 67 per cent. This percentage has rapidly increased as the facilities
provided for obtaining motors have been realised and appreciated by
the public, and as the charge for current has been reduced to the
existing rates of 2d. for intermittent use, and id. for continuous use,
until, in 1902, it stood at 49'25 per cent.

The gradual increase in this branch of the supply is set forth in the
following table, which also shows the improved load-factor of the
generating station.

622

CHATTOCK: MOTIVE POWER SUPPLY

[Leeds,

Year.

1893.

Molors on the Supply, Dec. 31st. On Hire
Motors on the Supply, Dec. 31st. Not on

Hire ,

Motors on the Supply, Dec. 31st. B.H.P. ...

Units sold for Motive Power

Total Units sold to Private Consumers

Percentage of Motor Units on Total Units...
Price charged per Unit for Motive Power...
Average Price per Unit obtained for Motive

Power

Load Factor, excluding Traction, per cent.

26
110

480,494
402
4id.

4-5d.
313

1896.

58
244

54.972

8x3,623

676

3id.

3-5d.
8-93

525

229
3460
1,297,120
3,012,158

4306
2d. & Id.

i-20d.
1174

1902.*

641

272

4,398

1,899,873

3,857,757

4925
2d. & Id.

I-I7d.
1378

* The figures for 1902 are approximately correct.

During these years it has been possible to reduce the charge per
unit for current supplied to the lighting consumers from 6d., in 1892, to
4Jd., less 2^ per cent, discount and a free supply of incandescent lamps,
in 1899. The price has stood at this figure up to the present date, but
the Corporation anticipate that they will be able to reduce it still further
in the near future.

In calculating the cost of generation of a motive power supply, when
this is combined with a lighting supply, the following points must be
borne in mind : — It is not necessary to increase the staff of men
employed in the station beyond what would be required for a pure
lighting supply. The management expenses, rents, rates, and taxes
remain the same. The plant installed in the generating station has to
be increased only very slightly, owing to the fact that the main part of
the motive power supply is discontinued at 5 p.m., before the peak of
the lighting load has to be met ; the part that does overlap, can be safely
and most economically dealt with, by slightly overloading the station
plant, for half an hour a day, for about six weeks during the twelve
months. The question of black fogs, of a density sufficient to necessi-
tate a supply during the hours of daylight, equal to the maximum
lighting load, has very.rarely to be considered, so rarely that it really only
affects one or two towns in the country. A fog such as is ordinarily met
with will not create a demand for more than 75 per cent, of the maxi-
mum lighting load, and it is found in practice that the motive power
supply can be satisfactorily dealt with by the plant installed.

The same considerations apply to the question of extending the
distributing network of mains. It is found that the majority of motors
installed, are connected to the existing network, which has been laid
for the supply of lighting consumers, and the current used by these
motors helps to utilise the mains during the hours of daylight. This is
a set-off against any small extensions that it may be necessary to
make to supply outlying power consumers. In some cases, however,
considerable extensions may be necessary ; these should be considered
separately, and if the estimated revenue from the current supplied does

1903.] FROM CENTRAL STATIONS. 623

not equal a certain percentage on the cost of the extension, the applica-
tion should not be entertained, unless, of course, the applicant is will-
ing to pay such a sum towards the cost of the extension, as will make
it remunerative.

The minimum percentage on the cost of an extension, that it is policy
to require, must be difiFerent in different towns, and can only be ascer-
tained by experience. As a basis to go upon, a percentage of lo per
cent, is suggested, this figure having worked out satisfactorily as regards
the City of Bradford.

It may be safely assumed, therefore, that the cost of generation
should not be estimated to include the following items : —

Wages in Generating Station.
Management, rents, rates, and taxes.

Standing charges upon the outlay in respect of station plant
and distributing mains.

The items which should be included are as follows, and these should
be taken at the full rate per unit for the whole of the supply : —

CoaL

Water.

Oil, stores, etc.

Repairs and maintenance of plant and mains.

Turning now to the considerations affecting the price to be charged.
It has, during the last four years, been the practice in Bradford to
charge one penny per unit for motors used continuously throughout the
working hours of the day, and twopence per unit for those used inter-
mittently. This method of charging has answered fairly well, though
it is open to several objections. For instance, some power customers
who use their motors intermittently consume a much greater number
of units per horse-power installed than others who have motors running
continuously ; again, it is often very difficult to decide whether the use
of a motor is intermittent or continuous.

The maximum demand system of charging is not so applicable to
motor supply as it is to lighting supply, on account of the fluctuating
nature of the load on a motor, and of the liability to sudden heavy over-
loads. The effect of these overloads is not necessarily felt by the gene-
rating station at the peak load time, but the reverse of this is rather the
case.

It would seem that the best method of charging is to base a sliding
scale charge per unit upon the number of units used per horse-power
installed per half year. Such charge might be graduated at id., ijd.,
2d., and a^d.

It is found that compared with a gas engine using gas at 2S. 3d. per
1,000 cb. ft, the cost of running a motor at id, per unit is considerably
less, in some cases the cost is half that of gas, in others the cost is
approximately the same. This, however, is owing to the motor being
set to drive long lengths of shafting where the load is fairly continuous
and heavy, an ideal drive for a gas engine. Where the load is subject
to great fluctuations, as is the case with crane and hoist driving, the

624 CHATTOCK: MOTIVE POWER SUPPLY [Leeds,

motor, even at 2d. per unit, shows a great saving over the gas engine.
This is owing to the facility for stopping the motor when not actually
in use, and starting again when required. It is found that this cannot
conveniently be done with a gas engine.

In order, therefore, to show a saving over gas at the above figure
per i,ooo cb. ft., the charge for current should vary from id. to 2d,
per unit.

The amount charged for rental should be kept as small as possible
consistent with paying actual expenses, and any profits required should
be looked for from the sale of current and not from the receipts for
rental.

The rental should include the following items : —

Interest upon capital cost of motors and other apparatus.
Cost of inspecting motors periodically.
Cost of maintenance of motors due to fair wear and tear.
Cost of depreciation on motors.

In the City of Bradford, for the year 1902, the cost of inspection and
maintenance of motors on hire amounted to ;£i,723, the H.P. of the
motors on hire being 2,996.

It would appear that an amount of 15 per cent, on the capital cost
of apparatus is sufficient to cover all liabilities in connection with a
hiring out department, and to allow sufficient margin for depreciation.

In conclusion, it is hoped that the figures and suggestions given in
this paper may be of interest to Central Station Engineers. They are
based upon actual experience in connection with the Bradford
Corporation supply, and should prove useful, especially to those
Engineers who are contemplating a motor-hiring department.

JJ^ ^ Mr. A. B. Mountain said that he agreed almost entirely with Mr.

Chattock. He was of opinion that a supply of 4,398 H.P. for motors was
larger than the supply in any other town in England, and the author
would no doubt say that the great success at Bradford was due to the
fact that this city had a large number of small trades.

Regarding the single-phase question the speaker thought that Mr.
Chattock was a little late in his criticism ; if he had made this
remark three years ago most people would no doubt have
agreed with him. In England there were about one thousand manu-
facturers of continuous-current motors, but few of them make
single-phase, and, probably, fewer still two- or three-phase motors.
There were thousands of persons criticising single-phase motors
and advertising continuous-current, but he did not think that it was
wise for them to allow themselves to be carried away. They had,
rather, to think of what was really right and suitable. He disagreed
with Mr. Chattock on this point very strongly.

Referring to the percentage (10 per cent.) allowed by Mr. Chattock
on the cost of an extension, he thought that there must have been an
oversight here. He did not consider that 10 per cent, would cover the
cost of the extension for mains, unless, of course, there were very special
consumers.

1908.]

FROM CENTRAL STATIONS: DISCUSSION.

Further, he did not think that the author had sufficiently brought
out the great advantage of electric motors over gas engines. There was
no doubt that, by getting rid of shafting, the power required in a place
was enormously reduced. For example : In a small works that he
recently visited they used to have a gas engine of i6 H.P., but they
now find that five H.P. in motors put on different machines would
do precisely the same work.

Mr. G. Wilkinson said Bradford was a pioneer town in electric
lighting and certainly showed the way in promoting the sale of elec-
tricity. Like the previous speaker, he was very much struck with the
second paragraph of the paper. It showed that Mr. Chattock had a
certain amount of pity for the community which has to put up with
single-phase motors. ,He himself did not share that sentiment. In the
first place he would like to point out how very much more reliable they
were than direct-current motors. Taking into consideration the fact
that the revolving part simply consisted of a mass of iron with short-
circuited conductors, the advantage certainly rested with the single-
phase machines so far as reliabiHty was concerned. The great drawback
at present, admittedly, was the want of a simple method of varying the
speed of single-phase motors. He had used this type for hoists, cranes,
printing machinery, and the like, and had found them very successful.

Mr. Chattock had stated that the load factor in Bradford, excluding
traction, was 1378. He presumed that this did not represent power,
but was simply the load factor relative to the motor business. From the
amount of the horse-power supplied, he thought that in Bradford many
of the motors were small.

Concerning the supply of electricity for large powers except for
intermittent work, there was a very formidable rival in oil engines. Mr.
Chattock gave a comparison between electricity at id. per unit and gas
at 2s. 3d. per 1,000 cubic feet, but he did not mention anjrthing less than
id. per unit for electricity. There were English oil engines made
which would give 5 or 6 H.P. for an hour for id., and there were
German engines, one of which he had under his control, working
daily for practically 16 hours, giving 9 B.H.P. for id. per hour. They
required a certain amount of labour and attention, but they had many
advantages. In the future we should have very keen competition from
oil engines. There were now firms ready to enter into contracts to
supply any quantity of oil as fuel at 35s. a ton.

With reference to the extension of mains in Bradford it appeared
that the charge was upon a basis of 10 per cent, on the capital outlay.
The paper did not indicate whether this was an annual charge or
whether it would run out when the interest and sinking fund expires.
It seemed to be a very reasonable figure, but further information
was desirable. Again, consumers who used their motors intermittently
appear to consume a much greater number of units than did regular
users, and it appeared that they must therefore have motors too large
for the work they have to do.

He quite agreed with the sliding-scale method as an equitable
means of charging for power, and was quite gratified to find that
15 per cent, was sufficient to cover the cost of a hiring-out depart-

Mr.
Mountain.

Mr.
Wilkinson.

626

CHATTOCK: MOTIVE POWER SUPPLY

[Leeds,

Mr.

Wilkinson.

Mr. Fedden.

Mr.

Churton.

ment, and thought it very reasonable and a charge that any consumer
could afford to pay.

Mr. S. E. Feddem said that he could join issue with the author
in regard to single-phase motors. He had installed motors up to 80
and 90 H.P., and lately one of 160 H.P., although he thought it
most likely that two-phase motors would be necessary for heavy
work. He had, however, no intention of abandoning single-phase
working altogether for small motors on present single-phase mains.

With regard to the question of variable speed he had never found
any demand for it.

They were in Sheffield following on much the same lines as in
Bradford, as they had in 1900 only 20 motors ; in 1901, 71 ; in
1902, 109 -; whilst this year they had 220, which amounted in all
to 1,400 H.P.

With regard to the price of energy, they had always had in Sheffield
a charge of 4d. a unit for lighting. Three years ago it was 2d. a unit
for power, and they then offered consumers lid. per unit, but nobody
would look at it. Finally they arranged to charge all-day consumers
ijd. per unit, with a id. per unit for all-day-and-night consumers.
If they used sufficient units to make up 50 per cent, of the horse-power
installed, they allowed them to come in at the ijd. rate. Gas being
only IS. 6d. per i,ocx) cubic feet, they had very keen competition.

He encouraged the laying of mains, but did not put on any price or
percentage, for the reason that the local price of gas was so low,
and their mains were past most of the houses and works. Referring
to the cost of generation, Mr. Chattock stated that rates and taxes
should not be included, but he thought that a certain percentage of
these charges, and also some standing charge on the distribution of
the mains, should be added to the cost of the unit in addition to the
items mentioned. He was rather surprised to see the figure given for
the maintenance of motors. The cost of maintenance appeared to work
out at about i is. 6d. per H.P. in Bradford. The motors averaged 47 H.P.
each. The cost of maintenance and inspection in Sheffield came to £7$
for the whole of the motors, or about 3s. per H.P.

He had not yet had the pleasure of a burnt-out armature, but was
looking forward to it.

Mr. T. H. Churton said that he had had an opportunity of making a
comparison of electric driving and gas-engine driving. In his works
he had a 6- H.P. Crossley engine and found that, at full-load, the cost
was little less than ^d. per H.P. hour, and at normal working load it was
about id. per H.P. hour. It was necessary, with a gas engine where
there was a variable load, to have an engine of considerably greater
power than was generally used, but in the case of a motor it was not so.
If a gas engine were overloaded it would pull up, but a motor could be
overloaded to a very much greater extent, before it will stop, especially
if it were a two- or three-phase machine. In his case a two-phase motor
was actually costing him less than the gas-engine did, although gas in
Leeds cost only 2s. 3d. per 1,000 cubic feet. Unfortunately there was
no convenient way of starting single-phase motors, and a method of
starting was required which gave really no trouble.

1903.]

FROM CENTRAL STATIONS: DISCUSSION.

627

Mr. Fynn.

As touching the competition between electric driving and oil Mr.
engines, it must be noted that motors could be placed where it
would be impossible to fix an oil-engine and there was also too much
work involved in the usei of oil engines, to say nothing of the smell
and noise.

Mr. V. A. Fynn thought the single-phase motors were not entirely
satisfactory. He had been familiar with them since 1893, when
they came out, and although he liked them, and was greatly interested
in their working, he did not think that they answered the present
requirements. In cases where only a few small motors were connected
to the supply mains, the power-factor question did not matter very
much. If, however, one were concerned with large powers, the matter
became more serious than was generally believed. At the Frankfort
Exhibition of 1891 a motor was actually shown which had a power-
factor equal to unity, although nobody seemed to have taken any
notice of it. The principle which was used in that motor he had lately
employed with various alterations and improvements in order to obtain
a power-factor equal to unity in a single-phase motor of his design
which he was bringing out, and which besides having a very great
starting torque, gave promise of the possibility of regulating its speed.
A 3 B.H.P experimental motor had been completed which started
with a loj H.P. torque and with a current simply proportional to the
full-load starting current.

Mr. W. Emmott said that Bradford had been worked for all it was Mr.Emmou.
worth with regard to motors. He could not speak from the Municipal
Engineer's point of view, but only from that of the Consulting Engin-
eer, and he thought it was a good lesson for some of the smaller
stations. Much depended upon the kind of man who was in charge of a
motor department. He considered that with a gas-engine running up
to 10 or 12 H.P. it was cheaper to put in motors at 2d. per unit. He
also thought that 15 per cent, was a large amount for maintenance.
For himself he thought 12 per cent, a fair and ample amount. He gave
some tests of the low thermal efficiencies of gas in various towns which
he had experienced, but as the gas companies were under no obliga-
tion to supply gas for power purposes, the consumer had no remedy.
This accounted for the large gas consumption per B.H.P. which he
had noted in many cases, and was all in favour of electro-motors.

Mr. W. M. RoGERSON thought that consumers using lifts and cranes
intermittently, say not more than half an hour at a time, should pay
more than consumers using power continuously.

Mr. H. Dickinson {Chairman) did not agree with Mr. Chattock
that it was unnecessary to increase the staff or plant for the full load.
If the orerlapping motor-load grew larger than the lighting load, he
would have to put in additional plant to keep up with it, and conse-
quently the staff would have to be increased accordingly.

Regarding the extension of mains, on a basis of 10 per cent, of the
revenue he thought this very small, and remarked that he would go
into some districts for one per cent., but not into others for ten per
cent, if there were no prospects ; therefore some little reservation was
necessary on that point. The consumers around the Works were made

Mr,
Kogerson.

Mr.
Dickinson.

628

CHATTOCK: MOTIVE POWER SUPPLY

[Leeds»

Mr.
Dickinson.

Mr.
Chattock.

equal to consumers in the outlying districts, unless there were a very
big margin between the selling prices. At Leeds they were selling
at cost price, as, last year, on a capital of £500,000, they made a profit
of only ;£3,ooo. He did not think he could afford to run to outlying
districts on a bare 10 per cent.

Referring to the units per B.H.P. for last year at Bradford, which
worked out at about 450 for every H.P. installed, he should like to ask
what sort of users they had, because these figures did not at all
correspond with those for Leeds. It was there found that they were
getting 800 units per H.P. installed. He did not know whether these
motors were for hoists, but he thought that Leeds seemed to be in a
very favourable position. In 1901 there were 205 H.P. installed ;
1902, 685 H.P. ; and there were now 1,363 H.P. The price in 1901 was
2d., less 5 per cent., and in 1902 it was 2d. to ij^. on a varying scale.
If the units were less then 360 per H.P. it was 2d., and on to 720 units
per H.P. installed. The average price obtained for motors was i^.

There were another 400 H.P. awaiting connection, and an application
for 500 H.P. to drive a rolling mill had been received,

Mr. R. A. Chattock, in reply, said that he had not had much expe-
rience recently with single-phase motors, but he had had a good deal
some time ago. He thought that the motors ran at a very excessive
speed, owing possibly to the high frequency that was in general use,
and that the efficiency of the motors up to about 10 H.P. was nothing
like that which could be obtained from direct-current motors. Com-
monly the starting current was excessive, and affected the general
supply in the neighbourhood, which was a very great objection.

He was surprised to hear 4hat Mr. Fynn and Mr. Fedden thought
that there were single-phase motors which would beat direct-current
motors.

The phenomenal increase in Bradford was not due to any special
advantages ; Bradford was an ordinary city, although there were many
trades in it. Power was mostly used for crane and hoist work, 4^ and
7 H.P. being the sizes commonly used. There were also a number of
larger motors (one of 60 H.P.) driving various classes of machinery,
printing works, large ventilating fans and refrigerating machinery. In
many cases these motors had been put in to replace gas engines, and
the reports of the saving in cost had been most satisfactory.

Referring to the amount of 10 per cent, on the cost of the mains,
this amount represented the actual revenue that should be received
from a proposed consumer, in order to make it worth while incurring
the cost of the necessary mains. If the amount per annum received
from the consumer equalled 10 per cent, on the cost of the mains
necessary to supply him, he considered that for any ordinary extensions
it was policy to connect up.

He agreed with Mr. Dickinson that for very long extensions in out-
lying districts this amount should be carefully considered, and' very
probably increased. In fact, he thought that, in getting out the cost
for each year, care should be taken to watch that figure and see that the
general percentage of revenue to the cost of the mains was not getting
too small. If it had a tendency to decrease, then the 10 per Q^nt shpuld
be increased in conformity with the general revenue.

19(».] FROM CENTRAL STATIONS : DISCUSSION. 629

As regards the cost of steam power, as compared with electric Mr.
power, he thought that from 150 to 200 H.P. could be more economi- ^***"'^'^
cally supplied by the consumer himself than by purchasing current
from a central station, that is to say, as long as such power was used
continuously throughout the working hours of the day. An engine of
200 H.P. was as economical as a very much larger engine in a
generating station, and there were no distributing charges to face in
connection with the steam supply. There was a charge for labour in
connection with the running of the steam plant, but from information
he had received from mill-owners who had gone into the question,
there was no doubt that they could produce steam as cheaply as
electricity could be supplied at id. from a central station.

With reference to the remarks on the load factor given, it included
the lighting consumer as well as the private power consumers, but it
did not include the power for tramways, although this came from the
same station.

Most of the motors ranged from i to 10 H.P. There were 15, 20,
and 60 H.P. motors in use, and there appeared to be an increasing
demand for the larger size of motor, as they were slightly more
economical.

He was very much interested in Mr. Wilkinson's remarks on oil-
engines, viz., that 5 or 6 H.P. could be obtained for id. an hour. He
took it that this was at full load, and that the cost of running an oil-
engine at a reduced load would be considerably more. The great
objection to oil-engines was the trouble in starting them and their
objection to be considerably overloaded, which was a special point in
favour of a motor supply. He also believed that Insurance Companies
objected to the storing of a large quantity of oil, and there had been
trouble in this respect. He thought that if oil-engines came into
general use the price of oil would go up. Some time ago he was trying
some oil fuel, and from the figures that were worked out he was satis-
fied that with oil at 2d. per gallon he could equal coal at about i8s. to
19s. per ton.

With reference to the question of continuous users of electricity
using less current than those using it intermittently, this was quite
possible. The continuous user very often ran his motor for many
hours in order to get it at id., because if he stopped his motor he was
charged at the rate of 2d. per unit. He thought it was best to base
a sliding-scale charge on the number of units used per H.P. installed.

With regard to variable speed, he had not found any great demand
for it. Possibly they had twenty or thirty motors, vaiying in size, in
which this had been asked for and obtained, chiefly for running special
machinery.

He did not agree that the cost of generation should include a portion
of the rents, rates and taxes, and a charge on the mains, although that
point should be watched. If the supply for motive-power purposes
very much exceeded the supply for lighting, the cost of generation
should be reckoned out to include more of the standing charges on the
station and possibly on the mains, but as pointed out the motor overlap
load was apparently very small at present, and in spite of the large

630 CHATTOCK : MOTIVE POWER SUPPLY. [Leeds. 1908.

Mr. increase in the number of motors, it did not appear that this should be

ciiattocic taken into account for some considerable time.

The figure that was quoted for the maintenance of the motors, viz.,
;£i,723, looked rather high, but it included many spare parts, and also
the supply of oil for running and general repairs, the cost of which was
refunded by the hirer. It was really men's wages for inspecting and
repairing the motors. The wages that were paid for inspection were
higher than was the case in many towns, and it was looked upon rather
in the form of an insurance. Every motor was inspected at least every
two months, and most of them once a month. He thought that the
benefit of it would be felt as time went on in the greater life of the
motors, because if they were left to look after themselves they were
liable to become very dirty. The consumer would not look after them,
and he admitted that the commutators were a source of trouble if the
motors were not looked after, consequently he did not think it a very
heavy item. He thought it would pay the alternating-current consumer
to look after his motors and to inspect them more frequently. Time
would show if this amount could be reduced by giving up inspecting
them so often, but at present he did not feel inclined to run the risk of
doing so.

Mr. Emmott thought 15 per cent, on the capital cost of the apparatus
was too great an amount to charge, and he recommended 12 per cent.
He (the speaker), however, thought that the 15 per cent, charge should
be made. The cost of motors during the last four years had dropped
by about 30 per cent., and if the charge were 12 per cent, it certainly
would not pay for the necessary inspection.

With reference to Sheffield beating Bradford he should be very
pleased if they got ahead, but he thought that if the question of the
H.P. installed per 1,000 of population were taken into consideration,
Bradford would still be able to keep the lead, although the increase
was not so great during the last two years. The increase in Sheffield
was rather phenomenal on account of the supply being specially pushed
just now. At the first everybody was coming on. Directly people
began to see that the motors could be obtained cheaply and were doing
well, they would all come on in a rush, and in a large town where there
was a great amount of power undoubtedly this rush would be felt
at first.

In Leeds, Mr. Dickinson said, they were getting 800 units per H.P.
installed. In Bradford, however, there were not many motors running
on a very heavy continuous load, the work being intermittent and
chiefly used in crane and hoist work. The staple trade in Bradford
was woollen, and all the mills had theif own steam plant. There were
not at the present time any motors in use for driving looms or wool-
combing machinery. It was found that the people applied for motors
for driving cranes and all small machinery where the load was inter-
mittent, and there was no doubt that this accounted for the sRiall
number of units that were used per H.P. installed.

HORIZONTAL AND SPHERICAL CANDLE-POWER. 631

ORIGINAL COMMUNICATION.

MEAN HORIZONTAL AND MEAN SPHERICAL
CANDLE-POWER.

By Alexander Russell, M.A., Member.

Introduction — Mean Horizontal Candle-power — How the Mean Horizontal
Candle-power varies with the Area of the Candle-power Curve in
Particular Cases — Mirror Effects of the Bulb — Rapid Methods of getting
Mean Horizontal Candle-powers — Mean Spherical Candle-power —
First Graphical Method — Mathematical Formula — Mean Hemispherical
Candle-power — Second Graphical Method — Rapid Method of getting
Mean Spherical and Mean Hemispherical Candle-powers— Conclusions.

The accurate rating of glow lamps, Nernst lamps, and arc lamps is a
matter of considerable commercial importance, and so the following
remarks on the mathematics of the question may not be out of place in
the Journal. The physical side of the problem, namely, the quality of
the light emitted and the best standards to use in the various cases, has
not been touched upon.

English manufacturers as a rule do not guarantee that an 8-candle-
power glow lamp gives a mean horizontal candle-power equal to eight
candles, but merely that the mean horizontal candle-power is within
20 per cent, or so of eight. They do, however, guarantee a certain
efficiency with particular classes of lamps, saying for example that their
efficiency at the start is 3*5 watts per candle, and that after a thousand
hours it is about 5 watts per candle. This method of rating lamps is
to be commended, as it cheapens the cost of production and is quite
fair to the consumer. By the candle-power of the lamp is meant the
mean candle-power in a plane perpendicular to its axis, and this candle-
power is also called its mean horizontal candle-power.

Mean Horizontal Candle-power.

If from a source S we draw lines equally in all directions in a plane
and make their lengths equal to the candle-power in these directions, then
the sum of all these lengths divided by their number gives the mean
candle-power in that plane. When the axis of the lamp is vertical, the
mean candle-power in the horizontal plane is called the mean hori-
zontal candle-power. Now many inventors have tried to increase the
mean candle-power in particular planes by means of reflectors and
refractors, and some even think that they can increase the total
quantity of light given out by the lamp by this means. As a proof they
mention that they have increased the area of the candle-power curve in
particular planes. This they have undoubtedly done in certain cases,
but it does not follow that they have increased the mean candle-power
in these planes. In fact, when we remember that by doubling the
intensity of the source we can quadruple the area of the candle-power
curve, the fallacy of their reasoning is apparent. The following mathe-
matical examples illustrate how the area and the mean value of the
radius of the candle-power curve can vary in certain cases.
Vol. 82. 42

632

RUSSELL: MEAN HORIZONTAL AND

If I be the mean value of radii
angular intervals in a plane, then —

Tn drawn at equal

1 =

r. + r, +

r, d9 + r.

tl9 4- .
nd9

4- r«

+ r., d9

2 IT
0

2 IT

Now, suppose
the candle-power
curve to be a circle
(Fig. i), and let S,
the source, be any
p>oint within it
We may suppose,
for example, that
the source is sur-
ounde d by an
absorbing cylin-
drical globe of
varying thickness
so that the candle-
power in the direc-
tion SP is repre-
sented by S P, and
that the locus of P
is a circle. We
shall find an ex-
pression for the
mean candle-
power for different
positions of S, sup-
posing always that the candle-power curve remains the same circle.

and C A = R, it is easy
to

Pig. I. — S is a source of light surrounded by an
unevenly distributing globe which makes the candle-
power curve in the plane of the paper the circle A PA'.
Any radius vector like S P gives the candle-power in
that direction.

^ circumference of ellipse

2 TT

Mean candle-power

If SP = r(Fig

I), PSA»=:0, CS = a, and(

show that—

r = a cos 0 -h >/ K= — a= sin ' 9,

/.2ir
rd9

Hence

1= ^

2 TT

r2^

1 V R' — a» sin - 9 d9

2 TT

circumference of ellipse

"~ 2 IT ~ *

MEAN SPHERICAL CANDLE-POWER.

633

Where the ellipse (Fig. i) has S for its focus and touches the circle
at A and A\

When S is at A,

and when S is at C

I=- . CA
= 0-637 . CA,

I = CA.

Hence, although the candle-power curves have all the same area,
yet the mean candle-power diminishes as S moves from C to A by
about 36 per cent.

It is easy to see from the mathematical definition of mean candle-

power that all curves of the family rs= a + bf{9\ where I /(©) = 0,

^ o
have *' a " for their mean candle-power.

Fig. 2. — S is the source of light, and S P
gives the candle-power in the direction S P.
Mean candle-power in the plane of the
paper equals the radius of the dotted circle.

Fig. 3. — S is the source of light, and
S P gives the candle-power in the
direction S P. Mean candle-power in
the plane of the paper equals the radius
of the dotted circle.

In the examples shown in Figs. 2 and 3, S is the source, and the
mean candle-power of S would be the same whether its candle-power
curves were given by the curves or circles shown. The equation to
the curv^e in Fig. 2 is —

r = a (i -f sin 9)y

and to the curve in Fig. 3 —

r = a (i + i sin 0).
In the first case the area of the curve is 100 per cent, greater than
the area of the circle, and in Fig. 3 it is 25 per cent, greater.

634

RUSSELL : MEAN HORIZONTAL AND

Graphical Construction.

When we have a polar diagram of the candle-power given, an
obvious graphical construction to find the mean candle-power is to
construct a new polar curve (see Fig. 6) so that —

then —

r, = r^f

Meail C.P. in given plane =

rde

2ir

J I r,« dB
J o

Area of new curve

^ ir

If the candle-powers are given as in Figs. 4 and 5, then the mean
horizontal candle-power is simply the mean height of the curve, ue.,
its area divided by its breadth.

DeGRC£S

Fig. 4. — Mean horizontal candle-power curve round a clear bulb 16 candle-
power glow lamp. Note the great rise of candle-power at 172 degrees due
to the bulb acting like a concave mirror and concentrating the light on photo-
meter disc. Distance of photometer head from lamp, about three feet.

MEAN SPHERICAL CANDLE-POWER.

635

Sufficient attention does not seem to be paid by practical men to
the extraordinary way in which the horizontal candle-power of an
ordinary glow lamp varies in different directions. In Figs. 4 and 5
are shown the results of the measurements of the candle-power of an
ordinary glow lamp taken at intervals of every five degrees in the
horizontal plane. The tests were made by two of my senior students,

Fig 5. — Mean horizontal candle-power on the other side of the same lamp.
Note the mirror effects at 240 degrees and at 350 degrees.

Messrs. Chubb and Morris, using a Lummer-Brodhun photometer, and
they paid particular attention to the points where the candle-power
altered rapidly. Their results. may be taken as typical of how the
horizontal candle-power of an ordinary glow lamp varies in different
directions. The sudden variations are caused by the far side of the
bulb acting like a concave mirror and concentrating the light on the
photometer screen. In order to determine whether it acted like a lens
or not a bulb was cut in two, but no trace of any lens effect could be
found. The mirror effect was very pronounced, an image of a distant
lamp being seen at a distance from the glass of about half the radius of
curvature. On taking an ordinary lamp in your hand and looking into
it with your back to a window two main images of the window will be
seen, one erect and virtual formed by the front part of the bulb, the
other Inverted and real formed by the back part of the bulb. It is the
back part of the bulb that causes the bright bands that can be seen on
the shades of glow lamps. On putting your eye in line with a bright
band coming from a glow lamp and moving it about, the image of the
filament will be seen to behave in exactly the same manner as images
do in concave mirrors. If a sheet of white paper be moved round it,

636

RUSSELL : MEAN HORIZONTAL AND

there will in general be positions in which bright bands of light arc
cast on the paper. Sometimes, especially in the case of n-shaped
filaments, there will be dark bands. These dark bands are caused by
one leg of the filament obscuring the light coming from the other leg.
A ten per cent, dip from the mean is by no means unusual in this case.

When glow lamps are to be used as substandards of light it is
necessary to test them first by finding their mean horizontal candle-
power curve. If the candle-power is not sufficiently constant for a ten
degree variation on either side of a given position, the lamp had better
be rejected. Having found a suitable lamp and having marked
distinctly and carefully the position in which it is to face the screen, it

Fig. 6. — Polar horizontal candle-power curve of glow lamp. The radius
vector S P gives the candle-power in the direction S P. Also S ^ = Js P,
and the area of the small curve divided by ir gives the mean horizontal candle-
power.

should then be run for a hundred hours, candle-power measurements
being taken at frequent intervals to get an idea of the shape of the life
curve. So far as constancy is concerned it is better to use low efficiency
lamps as standards, and if care is taken that the pressure applied to
them is never greater than the marked pressure and a record is kept of
the time they are kept burning during tests, they will be found most
satisfactory.

MEAN SPHERICAL CANDLE-POWER.

687

In Fig. 6, a polar curve of the candle-power of the glow lamp
illustrated in Figs. 4 and 5 is shown. The mean horizontal candle-
power was found by constructing a new curve, the lengths of whose
radii are the square roots of the corresponding radii of the candle-
power curve. The area of this curve divided by v gives 13*5 as the
mean hemispherical candle-power of the lamp, a result which was
verified by taking the mean height of the curves shown in Figs. 4
and 5.

As a rule, not much attention is paid to the mean vertical candle-
power of ordinary glow lamps. The curve shown in Fig. 7 may be
taken as typical.

Fig. 7. — Vertical candle-power curve
of ordinary glow lamp.

Fig. 8. — Vertical candle-
power curve when a spiral
glass rod twisted into the
shape of a cup is placed
round a glow lamp.

In Fig. 8 is shown the vertical candle-power curve of this lamp when
a spiral rod twisted into the shape of a cup is placed round it. The
shape of the candle-power curve is altered, but the change in the mean
vertical candle-power is very slight.

Rapid Methods of Getting the Mean Horizontal
Candle-Power.

When the lamp is rotated, the centrifugal force alters the position of
the filaments and generally alters the mean hemispherical caudle-
power. There is also a risk of the filaments breaking. Still, for
rough measurements, the method is a good one.

Another method is to use four equal pieces of looking-glass cut from
the same strip. Two of these pieces inclined to one another at 120

688

RUSSELL: MEAN HORIZONTAL AND

degrees are placed behind the standard lamp, and an exactly similar
arrangement is placed behind the lamp being tested. If then the

candle-power of the lamp being
tested is approximately the same
as that of the standard and the
mean horizontal candle-power of
the standard is accurately known,
we get by one reading an ap-
proximation to the mean of three,
and so time is saved. Great
accuracy, however, is not obtain-
able by this method if only one
reading is taken, as variations of
five per cent, can be obtained
by rotating the lamp into
different positions, these varia-
tions being mainly caused by the
positions of the bright bands.

Experiments were made
with diffusive reflectors, but in
no case could we make sure of
obtaining a five per cent, accu-
racy by one reading. Better
results would probably be ob-
tained by using uniform ground-
glass cylindrical chimneys to
put round the tamps when being
tested.

Mean Spherical Candle-
power.

If we draw from the source,
equally in all directions, lines
whose lengths are proportional
to the candle-power in these
directions, then the mean value

of the lengths of all these lines is the mean spherical candle-power.

If ^1, ra . . . r„ be the intensity of the light in the various directions,

then —

Fig. 9. — The revolution of SPA
about S A produces the candle-power
surface. Make a new curve S p a so
that S ^ = l/^T. Then the mean

■? V

spherical candle-power = ^— , where

4 *"
V is the volume generated by the
revolution oi Sp a round S a. Mean
spherical candle-power = 0125 S A.

M.S.C.P. =

r, -h ^2 +

+ rn

^ r dut

where du stands for a very small solid angle.
Hence, if we construct a new surface so that—

Tj^:: rh*

MEAN SPHERICAL CANDLE-POWER.

M.S.C.P. =

then —

47r'

where V is the volume of this new surface.

It will be seen that an exact solution of the general problem is
complicated. When, however, as is generally permissible in practice,
we may suppose that the extremities of all the lines representing the
candle-powers lie on a surface of revolution, various simple graphical
methods may be given to find the main spherical candle-power.

Fig. 10. — S P A is the polar curve of candle-powers in directions
below the horizontal in a vertical plane. If the top polar curve be
similar, then the mean spherical candle-power = 0589 Si4.

First Graphical Method.

We first find by experiment the polar curve SPA (Fig. 9), whose
revolution produces the candle-power surface. We then construct
a new curve S^a so that —

S^ = SP^-

It follows that the—

S P rfu> + . . .

M.S.C.P. = ■

47r
_ S^3 rfitf -h . . .

= 3V
4ir

= -3- X 2 TT A X Area S/> o,

4ir

where h is the perpendicular distance of the centre of gravity of the
area Spa from SA«

640

RUSSELL : MEAN HORIZONTAL AND

For example, in Fig. 9 the curve Spa is a circle. Hence in this
case the —

S.C.P. = ^^ X 2 IT ( -- ) X - ( — -J

47r ^3^/ 2X2/

= 1.SA.

Similarly in Fig. 10, where Spa is a circle (only half the curve is
drawn) —

M.S.C.P. = — X2irRXirR='
47r

= 15^3

= i^SA
16

= 0*5890 S A.

^^^^ — ""■^— — — _

w-^r

\ \/^

-V

'^'i

Fig. II. — Construction for finding the directions
in which to measure the candle-powers whose
mean value will give us the mean spherical candle-
power. S At the lower radius of a circle, is divided
into any number of equal parts, and through the
middle points of these equal parts lines are drawn
perpendicular to S /I. S Pt^ S Pa, etc., are the re-
quired directions.

Another Expression for the M.S.C.P.

With the source S as centre, describe a sphere (Fig. 11) of radius R.
Divide the vertical diameter of this sphere into any number of equal
parts, and through the points of section draw places perpendicular to

MEAN SPHERICAL CANDLE-POWER. 641

this diameter, then these planes will intersect zones of equal area on
this sphere. This follows from elementary mensuration, since the area
of the zone of a sphere is 2 ir R /r, where h is the perpendicular distance
between its two bounding planes. Now, if we take the mean value of
the candle-powers in the directions of all the radii drawn to one of
these zones and do the same for all the others, the mean of all these
results will give us the mean spherical candle-power.
For the case of a surface of revolution, if R = w // —

M.S.C.P. = ""^ + "^Jt---- + ''-
211

— 2R

" 2R*

Now A = R tfO cos 9,

M.S.C.P. = i rco^QdQ

~ 2

2
which is a simple formula.

For example, if the polar curve of candle-power be the semicircle
of spa in Fig 9, and a similar semicircle above the horizontal, then

the M.S.C.P. = 0-5.8 o.
Similarly, if it were the circle half of which is shown in Fig. 10,

M.S.C.P. = i 2R

the M.S.C.P. = i 2 R . cos'Bde

= 07854 . S o.

The equations to the curves shown in Figs. 2 and 3 are of the
form —

r ^ a -h 6 sin 0.

Hence the M.S.C.P. of the surfaces of revolution of which they are
sections —

IT
2

(a -\- b sin 9) cos 9 d9

=»J(

642 RUSSELL: MEAN HORIZONTAL AND

The curves shown in Fig. 12 arc parts of circles ; in this case —

M.S.C.P. = 0-555 • O A.

In Fig. 2 the ratio of the two hemispherical candle-powers is as
one is to three.

Mean Hemispherical C.P.

In this case we only take the mean value of the candle-power over
a hemisphere. The formula is —

r '

H.C.P. = xd9,
J 0

For example, in Figs. 2 and 3-

Upper H.C.P. = a — i 6.
Lower H.C.P. = a + i 6.

Fig. 12. — The revolution of the polar curves
shown, which are parts of circles, gives us
the candle-power surface. Mean spherical
candle-power = 0555 OA.

Second Graphical Method.

Having given the polar curve of candle-power APBC (Fig. 13)
construct a new curve so that—

MEAN SPHERICAL CANDLE-POWER,
then the area of this new curve gives the M.S.C.P. For —

613

Area

of Curve = i I o

p' dB

TT
2

/• + -.
= i xdB , z=z M.S.C.I

Fig. 13.— O is the source of light and AP BC\^
the polar curve of candle-power. Make O p =i
J~d N and construct the curve locus of p. The
mean spherical candle-power ^ the area of the
small curve.

Rapid Methods of Finding M.S.C.P.'s.

The following approximate methods will be found of practical value.
The theory will be best understood by considering a particular case.
Divide a sphere described round the source as centre into eight equal
zones (Fig. 11). Through the centres of the equal parts into which the
radius is divided draw perpendiculars meeting the surface in P„ P,, P3,
and P4 respectively, and suppose that corresponding lines are drawn for
the upper hemisphere. Then we may assume that the candle-powers
in the directions S P„ S P., etc., are all equally important

644

Hence

RUSSELL : MEAN HORIZONTAL AND
M.S.C.P. = ^ t.^-_+_i - +_^B.

where r„ r, . . . are the intensities of the light in the directions
S P„ S Pa. . . . The lower hemispherical candle-power would be given
by the approximate formula —

Lower H.C.P. =

— ^» + ^» + ^3 H- r^

If we find the angles of depression, S P„ S P, . . . once for all, then
we can take these as standard directions. The mean spherical candle-
power can be got directly by this method without any graphical con-
struction.

If the lower radius be divided into* 2 n portions, then the angles are
given by the equations —

cose. = i--.

Cos Oa = I —

Cos 0„ = I —

2«

2W — I I

2 « 2n

If radii be drawn making angles ± G„ with the horizontal, and if l„
and V^ be the intensities of the light in these directions, then —

M.S.C.P. =

I. + I. +

+ I,' + I,' +

Ix + I, +

Upper H.C.P. =

Lower H.C.P. = ?i' ± ^^^]>-' ' '.

The following are the values of 0„ 9,, etc., when 2, 4, 6, 8, 10, or 20
measurements of candle-power arc to be made : —

r—

Number of
Measurements.

Angles of Depression or Elevation from Horizontal in Degrees.

14-5, 48-6

96, 30, 56-4

7-2, 22, 387, 61

57, 17-5. 30. 44*4» 64*2

2*9, 8*6, 14-5, 2o*5, 267, 33-4, 40-5, 48-6, 582, 71-8

MEAN SPHERICAL CANDLE-POWER.

645

Approximations to the mean spherical candle-power of any required
accuracy can thus be obtained by measuring the candle-powers in the
directions of the angles given above and taking the arithmetical mean
of the results.

In order to illustrate the accuracy of these approximations the
following numerical examples have been worked out : —

In Fig. lo the lower hemispherical candle-power of the polar curve
SAP comes out as follows : —

Number of Measurements.

Lower H.C.P.

06495

0-5979

0*5924

05904

0-5901

' 0-5893

Infinite

05890

The first approximation is simply got by measuring the candle-
power at 30 degrees, the next by taking the mean of the values at 14*5
and at 48*6 degrees respectively, and so on.

In this case the mean of the candle-powers in directions 9*6, 30 and
56*4 would have been sufficiently accurate.

The following are the approximations to the lower hemispherical
candle-power of the polar curve S P A in Fig. 9.

Number of Measurements.

Lower H.C.P.

01 250

0-2188

02359

02422

0*2450

0*2500

Infinite

0*2500

646 RUSSELL : MEAN CANDLE-POWER.

Many other examples have been worked out, and it has been found
that the mean of five observations at angles of 57, 17*5, 30, 44*4, and
64*2 are quite sufficient for practical requirenients.

Even, however, when theoretically-accurate methods like Rousseau's
or the graphical methods we have described are employed, it is always
best to measure the candle-powers in the directions given above for the
tenth .approximation and not at ten equal angular intervals, because in
this latter case undue importance is attached to measurements at 60, 70
and 80 degrees. As a rule, an error in the measurement when the
angle of depression is ten degrees is much more serious than when the
angle of depression is eighty degrees.

The points to which attention is called in this paper are the follow-
ing :—

1. The bulbs of glow lamps act like concave mirrors producing
bands of light in particular directions. Dark bands are produced when
a vertical portion of the filament is parallel to another portion of it-
These effects produce very rapid azimuthal variations of the light.

2. In determining the mean hemispherical candle-power of glow
lamps, when no reflectors or diffusers are used, a large number of
observations must be made. This number may be reduced by using
suitable reflectors or diffusers. If we rotate the lamp, besides the risk
of the filament breaking, tbe centrifugal force must alter its shape, tluis
altering the total distribution of the light in space.

3. When glow lamps are used as standards it is of vital importance
to study the horizontal candle-power curve before choosing and mark-
ing the direction in which they are to face the photometer screen.
Neglect of this precaution even with c\-fi\a,mGnt lamps leads to large
errors. As a rule the plane of the filament is perpendicular to the
axis of the bench. The mean horizontal candle-power curves got by
comparing a lamp with two standards of different powers may show
distinct variations due to the relative mirror effects of the bulb being
different at varying distances of the photometer screen from the lamp.

4. Several simple formulae and graphical constructions are given for
determining the mean spherical and the mean hemispherical candle-
power of sources of light.

5. The simplest practical method of determining the mean lower
hemispherical candle-power of an arc lamp is to measure its candle-
power in directions making angles of 57, 17*5, 30, 44*4, and 64*2
degrees with the horizontal, and taking the mean of the results. The
easiest way of drawing these angles is by the graphical construction
indicated in Fig. 11. If greater accuracy is required, the same thing
can be done in several vertical planes passing through the axis of the
lamp and the mean of the results taken.

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Vol. 32. 1903. No. 162.

GLASGOW LOCAL SECTION.

A STUDY OF THE PHENOMENON OF RESO-
NANCE IN ELECTRIC CIRCUITS BY THE
AID OF OSCILLOGRAMS.*

By M. B. Field, Member.

(Paper read at Meeting of Section, February io//r, 1903.)

Three factors are generally essential to enable an intelligent in-
vestigator to satisfactorily complete any experimental research, viz.,
time, inclination, and apparatus.

During the last two years I have been in the enviable positioa of
having at my disposal plant and apparatus, from which by careful
study many important and, I believe, little understood phenomena
might be investigated. The inclination on my part to make the best
use of the opportunity afforded certainly was not wanting ; but the
small quantum of available spare time has hindered me from bringing
to a satisfactory termination several investigations on which I have
been at work.

As in future I shall not have in the same way facilities for con-
tinuing this work, I venture to lay before you in all their incomplete-
ness certain results I have arrived at, and to ask you to consider these
as mere suggestions, which may act as an incentive to some other
fortunate investigator, who may have the time, apparatus, and inclina-
tion necessary for completing the work.

My subject is more particularly some aspects of electrical resonance
which occurred to me on observing the shape of the E.M.F. wave of
the 2,500 kw. generators of the Glasgow Corporation Tramways
Department. These curves were depicted on the tracing desk of one
of those beautiful instruments invented by Mr. Duddell, viz., the high
frequency pattern of oscillograph.

* This Paper was also read in abstract in London on March 12th, 1903,
and was discussed jointly with Messrs. Constable and Fawselt's Paper,
** Distribution Losses in Electric Supply Systems," at Meetings of March 12th,
26th and April 23rd, 1903. See pages 734, 740, and 762.
Vol. 82. 43

648 FIELD : A STUDY OF THE PHENOMENON OF [Glasgow,

At first I contented myself with merely tracing on paper the curves
thrown upon the desk of the apparatus. When, however, I wished to
obtain curves which were to play an important part in some of the
official tests of the Glasgow plant, I considered this method too
inaccurate, and had constructed several special dark slides in which a
bromide paper or sensitive film could be stretched round a glass
shaped to the proper curvature, and by means of which records could
be taken photographically and the human element obviated. These
dark slides were cheap to construct, and very useful, and were used
almost entirely in the experiments I am about to describe.

.*. * f *-

W~ ttB

iji

..9 ± JL •.!_

.!r

•e

Fig. I.

Fig. I is a drawing of the dark slide, which is self-explanatory. In
using these, of course, all stray light must be screened off to obtain the
best results; and in this connection I found it useful to employ a
screen (S, Fig. 2) to cut off all light from the bright lacquered parts of
the oscillograph. Many of these parts are best painted with a dead
black paint, while it is of the highest importance to entirely cover the
bright steel face containing the saw-cuts in which the vibrating strips
are set. I found it advantageous to make several slight modifications
of this kind in the apparatus as supplied by the makers in order to
obtain the best results with the dark slides above mentioned.

19(^0

RESONANCE IN ELECTRIC CIRCUITS.

649

It may be of interest to call attention here to a few of the idiosyn-
crasies of the type of oscillograph employed.

In the first place, I experienced considerable difficulty due to the
shifting of the zero of the vibrating mirror. The apparatus contains a
fixed mirror which gives a fixed zero line, and it is necessary to adjust
each of the vibrating mirrors so that the base line (they project when
no current is flowing through them) coincides with the fixed zero line.
After the strips have been in circuit for a short while, however, I found
frequently that the zero line had shifted, which produced the apparent
result of larger positive half-waves than negative half-waves, or vice
versa. Again, there is a tendency for the cam which vibrates the
mirror to wear, and the greatest wear occurs towards the end of the
motion, since here the pressure on the cam is greatest. This wear
afiFects the horizontal, but not the vertical, displacement, the latter still
being directly proportional to the current flowing. In some cases,
therefore, where the positive and negative Half-waves were obviously

Fig. 2.

identical, I foimd it advantageous to apply a correction in the follow-
ing way : — Two lines were drawn parallel to the fixed zero line touch-
ing the highest point of the positive and negative waves ; the distance
between these lines was halved and a corrected zero line drawn in ;
the positive half- wave was then reversed and substituted for the
negative half, thus almost entirely eliminating the above-mentioned
effects. This, of course, would not be permissible where the positive
and negative half-waves were of different shape. I may say that all
the curves here reproduced have been uncorrected in this manner.

Another difficulty I experienced was due to the violent hunting of
the oscillograph motor when running under abnormal conditions.
Under these circumstances two distinct waves would be apparent on
the photograph, representing the limiting positions of the actual wave
which the projection of on the screen was shifting backwards and
forwards with great rapidity, instead of being stationary, as it should
have been.

Sometimes this hunting was caused by the variation of load on the
oscillograph motor (the tension of the spring controlling the mirror
varying from zero to a maximum in each revolution).

Curve I. represents the E.M.F. curve of the system under normal
load conditions, with one 2,500 kw. generator only running on the load,
and supplying 245 amperes per phase. The generators are 6,500 volt,
3-phase, 75 r.p.m. macHines, with stationary armatures having two

650 FIELD: A STUDY OF THE PHENOMENON OF [Glasgow,

slots per pole per phase, and 40 poles. Curve I, as also practically all
oscillograms reproduced in this paper, was taken from the low-tension
side of a bank of transformers in one of the sub-stations ; there were
thus a bank of transformers and a high-tension 3-core cable intervening
between the oscillograph and the generator terminals.

I fully recognise that it would have been more to the point had
some of my measurements been made in the high-tension circuit itself.
I even constructed a resistance to insert in one of the legs of the

Fig. 3.

Curve I. — E.M.F. Wave of Generator
on normal traction load, 245 amps, per
phase.

armature winding, and took a tapping off one of the coils near the
neutral point, as shown in Fig. 3. It was my intention to connect the
neutral point of the generator to earth during these experiments in
order to secure safety, it being normally insulated from earth. I had
not, however, the same facilities in the power-house as in the sub-
station, and unfortunately did not conduct any experiments in the
former place.

The arrangement generally adopted was that shown in Fig. 4 —

Fig. 4,

The transformer groups consist each of three 200 kw. single- phase
transformers connected A — system, and loaded on rotary converters.
The high-tension cables are as follows ; —

To Sub-station A

4 — 3-core

•15 in.

Length

= 4849 yards each.

4 — 3-core

•I in.

„

= 4i775

i»

4 — 3-core

•I in.

= 5>899

4 — 3-core

•I in.

= 2,286

4 — 3-core

•15 in.

^5i6o5

An examination of Curve L will show at a glance that there are
harmonics of a high order present in the wave form. Curve II.

1903.] RESONANCE IN ELECTRIC CIRCUITS. 661

represents the voltage and current wave forms taken from the low-
tension side of one of the 200 kw. transformers partially loaded on a
water resistance. It will be noticed
that for clearness the current wave
has been reversed, that there is
apparently no phase displacement,
and that the harmonics of the
current wave follow closely those
of the E.M.F.

Assuming we can represent the
E.M.F. wave by the expression

E =r 2 E, sin (2 ir / n / + e-,) . . (i) „ Curve II.-E.M F. and Current
^ ^ ' Waves from Transformer on water

n being the natural frequency of the ^o^^-
system, i.e., 25 cycles per second,

and the summation being extended to all terms obtained by giving i
successive integral values from i upwards, then the true voltmeter
reading of E, or the effective volts, will be —

yn? (2)

^ 2
and provided the water load acts as a true non-inductive resistance,
and one without capacity, i.e, provided no periodic storage and dis-
charge of energy occurs in the water resistance, the current will be
expressed by —

■j^ 2 Erf sin (2 IT J w / + ^0 (3)

and the true ammeter reading by 5V y^ (^^

The products of the ammeter and voltmeter readings will then be —

/r2(E.') (5)

The instantaneous value of the watts, obtained by multiplying the
instantaneous values of voltage and current strength, is —

i|sE,sin(2xi»/ + e,)p (6)

the average value of this, or the true wattmeter reading, is, of course,
again represented by the expression (5) ; in other words, if the load be
a pure ohmic resistance, the product of true volts and true amperes
represents true watts, no matter how irregular the wave-shapes may be.

Now the value of (2) may be obtained from the oscillogram of the
voltage, by taking the square root of the average value of the squares
of a number of equi-distant ordinates.

Similarly the value of (4) may be determined from the current
oscillogram.

Multiplying these together we obtain the value of (5).

The average value of (6) may be determined by first multiplying
the ordinates taken from the current and voltage oscillograms, and then
taking the mean.

662 FIELD: A STUDY OF THE PHENOMENON OF [Glasgow,

To test the water load, as also the oscillograph, I obtained arith-
metically the values of (2), (4), (5), and the average value of (6), as
described from the oscillograms, and in every case obtained agreement
within I 'per cent.

It is clear that, had the load possessed any properties of the nature
of self-induction or capacity, or if such factors existed in the oscillo-
graph itself, such agreement would not have been obtained.

It was natural to inquire what effect the harmonic or ripple in the
E.M.F. wave would have on the voltage at the rotary D.C. brushes.
To show this, I drove the oscillograph motor from the rotary slip-
rings, connecting one strip across the D.C. brushes, and one strip
between one slip-ring and one D.C. brush (see Fig. 5).

The result was Curve III. A distinct ripple was observable in the
D.C. voltage under normal load conditions, and by comparing it with
the wave length of the undulating wave we find the number of ripples

fOOCH

000-^^^*— 0000 — H^

Fig. 5.

Curve III.— D.C. Voltage of
Rotary on no Load and E.M.F.
between one D.C. brush and
slip-ring.

in the D.C. voltage per period is 12 ; in other words, there is an
alternating E.M.F. of 300 cycles superimposed upon the D.C. voltage
of 500 volts.

It is clear that the E.M.F. between one slip-ring and one
commutator brush will be an undulating E.M.F. either wholly positive
or wholly negative. If the negative D.C. brush is at zero potential,
and provided the rotary is on load, and the brushes are in the neutral
position, clearly every other point in the armature, if not at zero
potential, must be between zero and the potential of the -h D.C. brush.
Now, each slip-ring becomes connected directly to the -h and — brush
alternately once per cycle, hence shape of wave.

Until I saw this experiment I had half doubts that the ripples in the
A.C. voltage were introduced by the oscillograph itself. When, how-
ever, I ran a rotary as a double current generator, self-excited, driving
it by means of its starting motor, the D.C. voltage shown by the
oscillograph was a perfectly straight horizontal line, and the A.C. wave
was entirely devoid of ripples except of a very much higher frequency
and small amplitude.* (See Curve IV.)

• From Curve IV. it appears as though there were 35 or 37 ripples per
period. It may be pointed out that the armatures of these rotaries are
six-polar, and have 108 slots, this apparently corresponding to the number of
ripples in the oscillogram.

19(».] RESONANCE IN ELECTRIC CIRCUITS. 668

The process of parallelling could be watched on the oscillograph
screen, and a most fascinating sight it is to watch the D.C. voltage
spring from the straight line to a wave with ripples along the whole
length, and then to see the main wave instantaneously straighten out,
the ripples only remaining as the rotary is pulled into the correct
phase. The instantaneous formation of the ripples on the A.C. curve
can in like manner be watched.

It was easy, however, to ciemonstrate the. existence of the D.C. ripples
independently of the oscillograph, and for this purpose I drdve one
rotary by an independent motor as a D.C. generator, and a second
rotary parallel with the power-station in the usual way. The two +
brushes were connected together, and the negative brushes through a
hot-wire voltmeter in parallel with a Weston. The excitation was
adjusted till the latter voltmeter read zero ; the hot-wire instrument
on the other hand indicated 12 volts. The latter instrument was, of
course, merely measuring the square root of the mean square of the
ripple.

This corresponds to a total fluctuation from crest to hollow of
34 volts, or, say, under normal running conditionSf 6*8. I have tried to
filter out the alternating component
of the D.C. voltage, and transform it
up, by passing it round one winding
of a static transformer, neutralising
the magnetic saturation created by
the D.C. component by a current from
a battery, but I have not succeeded
in doing it. Curve IV.— E.M.F. Curve of

If I could have borrowed a 500- Rotary as A.C. Generator,

volt accumulator battery in order to

oppose it to the D.C. voltage of the rotary, I think I could have
obtained a considerable 300-cycle current through the battery. As I
shall show afterwards, I am able to accentuate these D.C. ripples
considerably under special circumstances.

I further observed the current flowing into the D.C. feeder circuits
of the tramway system, but could find practically no trace of a ripple
at all. The loss in outside circuits due to the ripple was therefore
negligible.

If we took the square root of mean square of the voltage ripple as
3 per cent, of 500 volts, and the current ripple in proportion, viz., 3 per
cent., and if we assumed that the whole of the A.C. component was
wasted in heat, ii would represent merely 9 units in 10,000. I am
therefore justified in saying that under normal conditions the loss due
to the D.C. ripple does not amount to i per mil.

There is no doubt that the source of these ripples lies in the teeth
of the generators, there being 12 teeth per period and 12 ripples per
cycle superimposed on the D.C. voltage. The ripples exist in the
high-tension voltage, pass through the transformers, through the
rotaries to the D.C. side, and if other rotaries be run as motors from
the D.C. 'bus-bar, the ripples reappear at the A.C. slip-rings. It seems
impossible to get rid of them by filtering them out. We have already

654 FIELD : A STUDY OF THE PHENOMENON OF [Glasgow,

disposed of the suggestion that they originate in the rotarics them-
selves. I think no one will venture to assert that the transformers
manufacture them. One way to decide that point would be to connect
the oscillograph direct in the high-tension circuit ; although I have not
done this, I have another proof (although to my mind no proof is
necessary), and that is, when one generator only is running in the
power-house the ripples are always present, though somewhat waver-
ing at times — when two generators are runrflng in parallel the ripples
often alternately appear and disappear with a regular periodicity
lasting several seconds. This is evidently due to the swinging of one

Curve V.— Current and E.M.F. of
Rotary on no load, under-excited.
Lagging current into rotary = 650
amps.

Curve VI. — Same as V., but over-
excited. Leading current into rotary
= 600 amps.

Curve Vll.—Current and E.M.F. of Rotary
on normal traction load, in parallel with two
others.

Curve VIII.— Current and E.M.F.
of Rotary on normal traction load,
in parallel with one other.

Curve IX.— E.M.F. and Current of
Rotary on no load, excitation ad-
justed to give minimum armature
current.

generator relatively to the other ; when exactly in phase the ripples
appear, when displaced by half the wave length of the ripple they
practically disappear. The same thing happens with the ripples
in the A.C. voltage. I have seen an almost rounded A.C. voltage
curve suddenly jump into peaks as one generator was switched out of
parallel.

Granting, then, that the generator E.M.F. wave possesses high
harmonics, and the back E.M.F. of the rotaries is a smooth wave (as
indeed one would expect from such a type of armature, and as is
shown to be the case in Curve IV.), it is evident that the rotary can
supply no back E.M.F. to equilibriate the ripples of the applied E.M.F.
What must happen in such a case is that when the opposing E.M.F.'s
do not balance owing to a ripple in the one and not in the other, a

1903,]

RESONANCE IN ELECTRIC CIRCUITS.

655

wattless — which I afterwards call a self-induction — current must rush
in or out of the rotary, which will absorb or equilibriate the difference
of voltage. Curves V. to IX. show this clearly. In the latter case the
rotary was running unloaded under condition of minimum armature
current. It will be seen that the amplitude of the ripples of the
current waves seems larger than that of the main wave itself, the latter
being scarcely distinguishable.

It is interesting to note that the current wave is rippled more
uniformly than the voltage wave.

The main drift of the first portion of this paper is to discuss the
conditions under which resonance may occur with one of the higher
harmonics of the E.M.F. wave introduced by the particular form of
toothed armature in use at the power-station. Let us first examine the
construction of the armature. Fig. 6 is reproduced from a scale
drawing of the armature slots, and field magnet pole-shoes. From an
examination of this figure it will be obvious that the magnetic flux must

niuinnj

lJ Li U Lj

Fig. 6.

be constantly shifting backwards and forwards along the pole-face as
tooth by tooth of the armature is passed. It does not necessarily mean
that the total flux through the field system fluctuates, but that this flux
emerges from the pole-face in "tufts" opposite the armature teeth,
and that these tufts of magnetism are dragged backwards, and spring
forwards along the pole-face according as the magnetic reluctance is
charged at different parts of the same by the change of position
relative to the armature teeth. The poles are champfered off so as to
avoid as far as possible change of total flux through the field system.
I do not think this goes on to any marked extent ; it would be possible
to detect such periodic changes by looking for fluctuations of exciting
current This could be done by suitably inserting the oscillograph in
the exciter circuit.* On the other hand, an examination of Fig. 6
would lead us to expect six more or less sudden irregularities or
excrescences per half-wave of the curve representing total threading
of magnetic fluxf by the armature coils. This does not mean a 12th

• I have tried this experiment under difficulties, and certainly detected
slight and rapid periodic fluctuations in the exciting current. The experi-
ment is well worth repeating, however, my results being by no means
conclusive.

t By threading of magnetic flux I wish to indicate the sum total of mag-
netic flux interlinked with each turn of the armature winding.

666 FIELD: A STUDY OF THE PHENOMENON OF [Glasgow,

harmonic ; afi even harmonic would be impossible with such a
generator— it would mean that the positive half -wave was of a diflEerent
shape from the negative half, and the right-hand half of each half -wave
was of a different shape from the left-hand half. This, of course, with
such a generator is impossible.*

If, however, we consider a smooth wave (not necessarily a sine wave)
with 6 ripples per half-period superimposed in the manner indicated
in Fig. 6a so that the ripples are wholly positive during the positive
half-period and wholly negative during the negative half-period, we

Fig. 6a,

should get a curve such as we might reasonably expect with a 12 slot
per period alternator. This curve of total threading of magnetic flux
would be quite symmetrical, and would possess 12 irregularities cor-
responding to the number of teeth.

It is therefore instructive to study this case, and to simplify matters
we will assume that the ripple between 0 and v can be represented as

• In making this statement I am leaving out of account all extraneous
effects, such as hysteresis in the armature teeth, cross magnetisation, etc.
Later on we fincf curves in which the right and left halves are different
owing to some such effects, in all probability. I mean here that, provided
the winding, slots, pole-pieces, etc., are symmetrical, the process of the flux
cutting into an armature coil must be the exact reverse of cutting out of a
coil ; moreover, the flux from an S-poIe must of necessity cut in and out in
the exact manner as does the flux from the N-pole.

1903.] ' RESONANCE IN ELECTRIC CIRCUITS. 657

a (i — cos 12 k t) and between «- and 2 ir as — a (i — cos 12 )fe /)• The
fundamental term is F N sin * / (F N being the maximum interlinkage
of flux with armature winding).

Now, we can quite easily split this up into a Fourier's series ; the
amplitude of the p^ sine term will be proportional to *—

/x (^) -/x (0),

and of the p^ cosine term to —

Where/, {k i) represents —

fci -cosi2^/)sin/A/ rf/or- i, cospki-\- cos (^ + 12)^/ ^
J pk 2 i^p -\' 12) k

cos (p — 12) kt

~~2XP — 12) * *

and /a (^ /) represents —

I (i — cos 12 kt) cos ^)fe/ <// or -?- sin /> * / - 5L"iA±J2)_^^ +
J pk "^ 2 p — 12) k

sin (^ — 12) AJ •
2 (/► — 12) k

If ^ is even, cos (^ ± 12) x = + i.

If p is odd, cos ()^ ± 12) IT == — I.

If p is odd or even, sin (^ ± 12) ir = o.

. • . /, (x) — /, (0) oc (^ — V, ^ ^ where ^ is odd,

^« (t) — /, (<?) = 0 „ even,

4 («•) —/a (0) = 0 „ odd or even.

This shows us that in this expansion the odd harmonics only enter
in, and they are all sine terms.

Now, ^//xa _ j^\ becomes infinite when / = 12, as /> can only
have odd integral values we see that the nth and 13th harmonics are
the most important.

The relative amplitudes of the harmonics in the expression for
E.M.F. are obtained from those representing total interlinkage of flux
by multiplying by the corresponding order of harmonic. This has
been represented in the following table : —

Flux.

E.M.F.

7th Harmonic, | + t,'^ = -215

150

9th

4 + A = -253

227

nth

T»T H- U = -568

6-24

13th

Vj— i'5 =-'444

-577

15th

tV- « =-119

-178

17th

Vt — ^:i\ = — -059

— i-oo

• The full expression is, of course —
{/. M - /i W } + I -/i (2 tt) +/, (x) I which in our case is 2 If, (tt) -/, (0)].

668 FIELD : A STUDY OF THE PHENOMENON OF [Glasgow,

We may say generally that the most important harmonics where
there arc q teeth in the generator per pair of poles are the

{q— i)« and the (^ H- i)^

unless indeed the grouping of the armature conductors is such as
would naturally introduce other harmonics of important magnitude,
independent of whether the armature be smooth or not.

The question now arises whether 12 ripples in the D.C. voltage per
cycle are consistent with an nth and 13th harmonic. I think so. If
we consider the 13th harmonic occurring similarly in the three phases,
A, B, C, then the harmonic in phase B will be 120 deg. of its own
period in advance of the harmonic in A. Similarly the harmonic in C
will be in advance of that in B by 120 deg. This means that we have
a true " three-phase ripple " advancing in the same direction as the
main wave, but with 13 times the velocity. Now, look at the nth
harmonic ; in phase B it will be 2/3 period in advance of that in A ;
similarly C will be 2/3 period in advance of B. This, again, will form
a "three-phase ripple," but retreating this time w|th 11 times the
velocity of the main wave. What does this mean in the rotary
converter ? The armature is rotating, say, at n revolutions forwards ;
the three-phase current in it produces a backward rotating field of
speed n relative to the armature, or at rest relativel}' to the field s)rstem.
The 13th harmonic, travelling 13 times as fast and in the same
direction, corresponds to a rotating field revolving at a speed of
(13 — i) times that of the armature relative to the fixed position of the
brushes, while the nth harmonic produces a field rotating in the
opposite direction, and therefore with (11 -f i) times the speed of the
armature relatively to the fixed frame of the rotary.

Both of these harmonics will therefore have the effect of producing
12 ripples per cycle in the D.C. voltage. The same argument could
not be applied to the 17th, 19th, or any other harmonics ; if, therefore,
for any reason these predominate, we should expect the D.C. voltage
line to be somewhat broken and jagged. In this connection refer to
Curves X and XII, and compare also the undulating voltages.

Again, if we assume that (due to the changing magnetic reluctance
of the circuit as the pole assumes different positions relatively to the
armature teeth) fluctuations in the total magnetism emerging from the
polar surface are introduced, we can imagine that the field system is
giving a rise to a constant, plus an alternating, flux. This alternating
flux will have a frequency of q where PU equals the frequency of the
generator. This alternating flux is, moreover, equivalent to two
rotating fluxes rotating forwards and backwards with q times the
velocity of the field system. If we add the rotation of the field system,
we have a main or fundamental field rotating at, say, unit speed, a
forward rotating field at 9 + i, and a backward rotating field at a
speed of ^ — i. Hence variation of total flux will likewise give rise to
the nth and 13th harmonics.

We now come to the question of 1 the magnification or accentuation
of the harmonics. This can be brought about, in my opinion, in two
entirely distinct and separate ways : —

1903.]

RESONANCE IN ELECTRIC CIRCUITS.

659

(i) By strongly magnetising the tcetli in the armature by the

armature currents themselves;
(2) By resonance, pure and simple.
These two causes produce results of a very similar nature, but each
phenomenon appears to require a totally different explanation.

AAAAAAAAAAAAAAA/W

Curve X.— A.C. and D.C. E.M.F.
of Rotary. Generator supplying 140
amps., lagging current.

Curve XII. — A.C. and D.C.
E.M.F.'s. One rotary running with
normal excitation, 93,700 yards of
cable connected.

Curve XIV.— Rotaries on no load
nver^excited, 185 amps., leading at
power-station.

\AAAAAAAAAAAAAAAA/N

Curve XL— A.C. and D.C. E.M.F.
of Rotary. Generator supplying 25
amps., 7 rotaries running on no load,
normal excitation, 93,700 yards of
cable connected.

Curve XIII. — Rotaries on no load,
under-excited, 195 amps., lagging at
power station.

Curve XV. — E.M.F. Wave of

Generator on no load, cables adjusted
for partial resonance with 13th har-
monic.

Examine Curves XI I L, XIV., XV. In the first case, a lagging
current,' nearly equal in amount to the full -load current of the
generator, was being given out.

Now, a lagging current involves a very strongly-excited field system
in the generator. The armature current will be of a demagnetising
order, and will produc its maximum effect when the pole is in the

660 FIELD : A STUDY OF THE PHENOMENON OF [Glasgow^,

most favourable position for the magnetisation of the teeth within
the coil.

A leading current, on the other hand, involves a weakly-excited
field system, the armature currents augmenting the magnetism due to
the field winding ; again the pole is in a favourable position for the
magnetisation of the teeth by the armature currents.

It appears, curiously enough, that the lagging current produces the
greater magnification of the harmonics, but that practically the full-
load current is necessary to produce this effect to any great extent.
Turn now to Curve XV. A few cables only were in circuit, and the
current flowing out of the generator was too small to be read on the
station instruments. This was a case of resonance.

I would here ask pardon for digressing into the elementary theory
of electrical resonance for the benefit of any present who may not
have had occasion to consider the subject.

F^G. 7.

The current flowing into a condenser may be expressed in effective
amperes bv

2irnKV (7)

where n = frequency of the circuit ;

„ K = capacity of condenser in farads ;

„ V = effective volts.

Again, if L be the coefficient of self-induction of a coil, the current
passing through it will be expressed by

(8)

2 7rnL
V being the effective volts at its terminals.

If we equate (7) and (8) we get the condition under which the
capacity current equals the self-induction current, V being the same in
each case. This condition is

(2 7rnY =

(9)

Let us suppose that we have a pure self-induction and a pure capacity
connected in parallel, as in Fig. 7.

Let the alternating E.M.F. V be represented by the vector O V ; we
know that the capacity current will be 90 deg. in advance of O V, that is

1903.]

RESONANCE IN ELECTRIC CIRCUITS.

661

in position OK; we also know that current flowing through the self-
induction will lag behind O V by 90 deg. This is represented by O L.

If now equation (9) holds, O K = O L, and the resultant of these
currents as far as the outside circuit is concerned, is zero at every
instant. We have then the case of a combination, of which the
terminals are a and b ; when this combination forms part of a closed
circuit in which an alternating E.M.F., of frequency n and value v,
is generated, no ciurent circulates on the outside circuit act, and
the potential difference between a and b is V. These are the conditions
which would hold if the combination were removed and a perfect
insulator substituted. We may therefore say that this combination
at this particular frequency behaves, as far as the outside circuit is con-
cerned, as a perfect insulator.

Now, introduce resistance r into each arm of the combination ,
and modify the diagram to suit, Fig. 8.

O L and O K will not now lag and lead by quite 90 deg. ; in each case
we have an ohmic drop O r in phase with the current, and an E.M.F.
O /, O )fe at right angles, such that the resultant with the corresponding
ohmic drop is O V.

The current in the outside circuit will be O^, which is equal to

0L«

2 X O L sin X ; or 2 r

and will be in phase with OV. The combination therefore will
behave as though it had an ohmic resistance of

P-Y! i_'
OL' ^ 2/'

Now,OV=0/»-f O;-'; O /« = (2x»L)' O L», and from (8) and

{9) we can write ?- for 4 iH* w*,

hence O V« = (t -h f) O L» .W. the resistance is JL + - .
K ' ' 2 Kr 2

66-2 FIELD : A STUDY OF THE PHENOMENON OF [Glasgow.

Let us take an example and put L = i secohm, K = i microfarad,
r = I ohm, then the resistance of the combination will be 0*5 megohm ;
thus we see that if the capacity and self-induction be not pure, but
contain also a small amount of ohmic resistance, the combination
behaves towards the outside circuit at the particular frequency as
an imperfect insulator, but nevertheless of high insulation resistance.
If in this particular case we make the further condition that

-4;^ + - = rorthatK=^,

the combination is equivalent to an effective resistance of r ohms, and
this will as a matter of fact be true not only for sine waves of the one
particular frequency, but universally for any periodic or unperiodic
function which expresses the change of V ; in fact, under these
circumstances the current in the outside circuit is always V/r.

We have now to consider a perfect self-induction in series with
a perfect capacity, and the same current C passing through each. This
modifies the diagram shown in Fig. 7 somewhat.

If we turn O L through 90 deg. forward, the E.M.F. required
to overcome self-induction will be O Vl ; if we turn O K back through

g/ 00(100 WOOWOOWOOOO ^^^— qi^bi , ^^

■e

Fu;. 9.

90 deg. to concide with O L, the voltage vector will take the position
O Vk ; see Fig. 9.

This diagram represents the state of things when the same current
flows through capacity and self-induction, and the current is at its
maximum.

If, therefore, the current is C, and is represented by the vector O L
and O K, the potential difference between a and d will be the vector
O Vl and between d and b the vector O V^ ; therefore between a and h
the potential difference will be the sum of O V^ and O V,. , which is at
every instant zero. We are therefore sending a definite current through
the combination, although no potential difference between the terminals
a and h is necessary. The combination, therefore, behaves, as far
as the outside circuit is concerned, at this particular frequency as
a perfect conductor. I am indebted to Mr. R. C. Clinker for the
notion of a perfect insulator and perfect conductor here introduced.
The current strength in the circuit acb will be determined by the
resistance of this portion of the circuit and the E.M.F. induced in it.
If the resistance be low, the current will rise to a correspondingly
high figure.

1903.]

RESONANCE IN ELECTRIC CIRCUITS.

663

Now, although the potential di£Ference between a and b is zero, we
know that that between a and dord and b is given by equations (7) and
(8). Let us therefore imagine the E.M.F. E acting in the circuit, the
self-induction short-circuited, and the current measured to be c ; then,
if the capacity be short-circuited instead of the selfrinduction, we shall
have again the current c flowing.

If both be short-circuited we shall have a current of E/p where p =
resistance of portion acb. Now, E/p may be 10, 100, 1000, etc., times c,
just depending on the value of p. But if both self-induction and
capacity remain unshort-circuited, the same current will flow as if
short-circuited : hence, in the former case the potential difference a d
or ab will be approximately 10, 100, 1000 times E, as the case
may be, just depending on the ratio of E/p to c. This is what is known
as electrical resonance, when the combination of self-induction and
capacity acts like a perfect conductor, or a nearly perfect conductor,
as far as the outside circuit is concerned, there being, however, a rise

of potential within the combination equal to C \/ ^ .

Of course, if we consider the self-induction as possessing resistance r,

Fig. id.

and the capacity also the same resistance, the combination will
behave as an imperfect conductor with ohmic resistance 2 r ohms, i.e.,
the potential difference between a and 6 will be 2rC and in phase
with C.

In alternating electric supply circuits we often have to deal with self-
inductions and capacities which would check the current down to the
same values if the same E.M.F. were applied to each, which is
the necessary condition for resonance ; consider, for example, a two-
phase cable with two insulated cores within a common outer as return ;
see Fig. 10.

Suppose phase B in the power-house has been opened, and consider
the state of things that exists ; we can represent it as shown in Fig. 1 1.
Current enters conductor a, and returns by conductor c ; it can
flow through the capacity a c, and the self-induction a c, these being in
parallel ; but an alternative path is through capacity a b, and thence
through capacity 6c in parallel with self-induction be.

Suppose the frequency is 25, the voltage per phase = 3000 volts, the

.transformers at the end of the line 150 kw. each, and such as to

take a magnetising current of 2 per cent, of full-load current or

one ampere ; secondary circuits are open. Let the capacity between

either conductor a or b and sheath, the other conductor being grounded

Vol. 82. 44

664 FIELD : A STUDY OF THE PHENOMENON OF [Glasgow,

be 75 mf . per mile, and between a and b together, and sheath '9 mf .
per mile, i.e, cap : (a + c), 6 = 75, and cap : (a + ^), c = 'g mf .
per mile, then we have a capacity effect equivalent to that shown
in Fig II. Let the length of line be 2*83 miles, then the total capacity
a c, = 1*27 mf. and total capacity a 6, =s -847 mf. If. now the potential
difference between b and c is V,, the current through the transformer
6 c is ^»/3ooo = .3*33 X ^^~^ V„ and through the capacity be, 2 x
10-^ V,. The current arriving at 6 will therefore be a wattless current.

lagging 90 deg. between the E.M.F. and equal to 133 io-< V,. But if
the difference of potential between a and b is V„ we have again a
capacity current through a 6 of 1*33 10-^ V,.

Thus we have the necessary conditions for resonance, and the
potential of the switched-out conductor b will rise until the insulation
somewhere in the cable gives way and modifies the conditions. This
has merely been given as an example ; there are, of course, a large
number of combinations possible where resonance might occur, and

smmmmu

Fig. 12.

every station engineer is more or less on the alert for them. A most
interesting paper on the subject of high-tension cable breakdowns from
resonance effects appeared in the •* Electrotechnische Zeitschrif t " on
28th December, 1899, by Mr. Gisbert Kapp, and was translated by the
present writer for the Electrical Rrview, and appeared in the 9th and
23rd March issues of that paper in 1900.

Now, every alternator possesses reaction and self-induction. By
reaction I usually mean that the armature currents produce magnetic
lines which thread through the magnetic path in the field system,
either weaHening or strengthening it, according as the armature
ampere- turns assist or oppose the field system magnetising force. The
term self-induction I usually apply to those lines of force generated by

1903.] RESONANCE IN ELECTRIC CIRCUITS. G65

the armature currents whigh do not produce an alteration of the total
flux in the field system, but which close round the armature windings
without including the field-magnet windings. Both of these effects are
more or less proportioned to the strength of the armature currents, and
result in an alteration of the magnetism threading the armature
windings. This diminution or increase, as the case may be, induces an
E.M.F. in quadrature with the current, and may therefore be looked
upon as a self-induction.

Every alternator, therefore, may be represented by an imaginary
machine producing an alternating E.M.F., without self-induction and
without reaction, but with a choking coil in series with it. Un-
fortunately, as we shall see later, it is necessary to consider the
choking coil as having a variable coefficient of self-induction, which is
however, a periodic function of time. We may thus represent a three-
phase alternator connected to a cable as in Fig. 12.

Fig. 13a. Fig. 136. Fig. 13c.

In talking of the self-induction of an alternator, I shall for the
purpose of this paper include in the term the armature reaction, ue., I
shall refer to that self-induction (whether with constant or variable
coefficient) which inserted in spries with a reactionlcss and self-
inductionless machine would give the same characteristics.

The capacity of a three-phase three-core lead-sheathed cable may
be considered as a combination of capacities, as in Fig. 13 (a).*

A three-phase A capacity as shown in Fig. 13 (6) will take the same

current per line wire as a Y capacity as in Fig. 13 (c) if K = .

3
We do not in practice meet cases where the self-induction of

• We are justified in assuming the capacity effect of a multiple core lead-
sheathed cable can be exactly represented by actual capacities between the
individual conductors, and between the conductors and lead sheath, for
taking the case of a three-core cable, we know that if Q, Q^. Q„ V, V^ V,
represent the charges and potentials of the various conductors, the lead
bheath being grounded, we have the relations—

Qi = fl... V, + a,., V, + <i.-5 V3 (10)

and similarly for Q, and Q3, where the a coefficients are constants of the
same dimensions as capacity.

Now, if we consider capacities K„ K,.,j K,^ connected between the con-

666 FIELD: A STUDY OF THE PHENOMENON OF [Glasgow,

the alternator will produce resonance with the capacity of the cable

system at the fundamental frequency. For example, taking a large

three-phase cable system as represented by a

three-legged capacity of 5 mf . per leg, the capacity

^^"'^ current per leg at 6,500 volts per phase, 25 cycles

^ -,— o4cr. would be 2*95 amperes. Fig. 14.

The self-induction in the alternator which
I ^,xk^^ would produce resonance with this cable system

^A^ /^^ would therefore be such as would only allow
2*95 amps, per leg to circulate when the generator
Fig. 14. was excited to 6,500 volts, and short-circuited.

Such an alternator would be manifestly in-
adequate in connection with such a cable system, but might perhaps

ductors, and K,a K,^ Kj^ connected between the conductors and sheath, wc
have : —

Q. = K,., (V, - V«) + K,., (V, - V3) -f K,^ V. . . (II),

and similarly with Qa and Q3.
This can be written as —

Q, = (K,., H- K,.3 + K„) V, - K,.. V, - K,.3 V3.

Hence a,., = Ki.a + K,.3 -|- K,^

- a,., = K,.a

- <i,.3 = Ki.j , and so on.

We therefore see that (11) is only another way of writing (10) ; if then
we determine K,., K,-3 K,^, etc., by experiment, we can consider these as
actual capacities connected as represented by eq. (11).

Owing to symmetry in a three-core cable we can write —

and K,^ = K,.3 = Kj^ = S.

Now, if 2 and 3 be earthed, we have —

Q, = (2 K + S) V, (12).

If 2 and 3 be connected together but not earthed, and if they together
have an equal and opposite charge to that on i, we have —

Q, = (2K-f-S)Vx - 2KV.

Q, = (K + S) Va - KV, = - 2£

.• V, = -^J,andQ, = (2K + |S)(V, - V») . . . (13).

Lastly, if 3 be left insulated without charge, and if the charge on 2 t)e
equal and opposite to that on i, we have —

Q. = (2 K + S) V. - K (V, + V3)
V = — V
and o' = (2K V S) V3 - KV, - K V„ ix., V3 = O.

Qx = (3K + S)V. = gK + |)(v. - V,) . . . (14).

If, therefore, we measure Q and the P.D. in any two of these cases, we
have all particulars necessary tor the determination of the capacity constants
of the cable, and can treat these as if they were actual capacities connected
as shown in Fig. 13(a), where the centre point is the lead sheath.

We shall have occasion to make use of (12), (13), and (14), a little later.

This gives

1903.] RESONANCE IN ELECTRIC CIRCUITS. 667

be used for applying a pressure test to the cables, in which case, of
course, the greatest care would have to be exercised.

Although the self-induction of the supply alternator will not
produce resonance at the fundamental frequency, it does not at all
follow that such may not occur, due to a higher harmonic of the E.M.F.
The current which a given capacity will take at a given voltage is pro-
portional to a frequency, while the current which a self-induction will
pass at the same voltage is inversely proportional to the frequency.

In the above case the capacity current per looo volts corresponding
to the nth harmonic would be 8*65 amps. A self-induction which
would pass 8*65 amps, at 1000 volts 275 cycles per second would pass
356 amps, at 3,750 volts and 25 cycles, or an alternator with this self-
induction per leg would give on short-circuit 356 amps, per leg when
excited to 6,500 volts per phase. (I have chosen this figure, because it
nearly corresponds with the results taken from the 2,500 kw. generators
in Glasgow.) We should therefore at first sight expect to obtain
resonance with such an alternator, and a cable system corresponding to
Fig. 14, if an nth harmonic existed in the E.M.F. wave.

I made some experiments to determine the capacity of the cables,
by inserting a hot-wire ammeter in circuit, but I obtained strangely
inconsistent readings ; I therefore forbear to give them.

Mr. R. C. Clinker made some tests on similar cables for the Central
London Railway, and obtained the following results per mile : —

1. From one core to other two cores -f lead sheath = '38 mf.

2. From one core to other two cores, sheath disconnected and
earthed = 32 mf.

3. From one core to one other core, 3rd-core insulated, sheath
disconnected and earthed = '23 mf .

If K be the capacity from core to core, and S the capacity from core
to sheath, and assuming the insulation of both poles of the testing
circuit to be so good that all leakage currents were negligible in
comparison with the capacity currents, we see that we have : —

By test (i) 2 K -h S = -38
„ (2) 2 K + ? S = -32
.-. S = -i8 K = -i

and by test (3) we have a capacity of

2^ + 2

Which with above values of K and S equals '24 as against '23 actually
measured.

The above cable is therefore equivalent to a Y capacity of '48
mf. per leg per mile, and therefore io'4 miles would give the
capacity represented in Fig. 14.

As a matter of fact, I find considerably more cable is needed
to produce resonance, and I think this is probably due to the fact
that the coefficient of self-induction of the alternator is by no
means the same for the fundamental as for the higher harmonics.

GGS

FIELD : A STUDY OK THE PHENOMENON OF [Glasgow.

We know that the coefficient of self-induction of such a machine
varies between wide limits, it must depend on the relative position
of field system to armature coils, and also on the value of the
armature current in each position. Fig. 15 represents what is known
as the curve of synchronous impedance of the Glasgow alternators ;
or the short-circuit armature current, in terms of armature volts
on open circuit with the same field excitation at synchronous
speed.

In the first place, it is clear that by this method the self-induction
should be a maximum, since the poles are in the most favourable
position when the armature currents are at their maximum. Next,
we see that even this method does not give a constant coefficient.
If we take the area of one-half period of the E.M,F. wave as
proportional to the square root of the mean square, and the maximum
of the current as proportional to the R.M.S., which would be correct

*»^

— -

■/

—

tfM

9tfP\

V i

HTl

QAH

£C-

TX A

ITMlif

— -

"-"-

•

r .

!f2

•

'Aa.

mnt

U '■

Fig. 15.

assumptions if we were dealing with sine functions, then the volts

would be proportional to, or represent maximum flux, and current,

the maximum current producing such flux, in which case the slope

</N
of the synchronous impedance curve represents -rp, where N is the

total flux produced by the current C.

Now -r-7^ = -Ti ' j7^, therefore the slope which we will call tan 9 is

such that

/>tan«_-=^-(orL_=EJ,

which means that tan 9 at every point of the curve is proportional
to the coefficient of self-induction for that particular current strength.

Fig. 15 shows that this varies between the limits of 1*3 at low
currents and 0-5 at 300 amperes.

We see then that the coefficient of self-induction has a different
value for each ripple on the E.M.F. wave, due to the position of

1903.]

RESONANCE IN ELECTRIC CIRCUITS.

the field system ; and, again, when a heavy armature current is being
generated, the coefficient is further modified by the degree of
magnetic saturation of the armature. The resultant of these two
effects must depend largely on the power-factor of the circuit, and
will be an extremely complicated function to express.

If we examine Curves XVI. and XVII. we see that with 93,700 yards
of cable in circuit we obtain the nth harmonic accentuated; with
somewhat less cable in I have obtained resonance due to the nth
harmonic, but could not obtain a photographic record. Curves XVI.
and XVII. were taken with about twelve months' interval. The
first was traced by hand ; the second photographed. I cannot vouch
for the engine speed being exactly the same in each case. On
reducing the capacity I brought the 13th harmonic gradually into
prommence (see Curves XVIII., XIX., and XV.). It is very difficult

Curve XVI.— No Load E.M.F.
Wave. 93,700 yards of cable con-
nected.

Curve XVII.— No Load E.M.F.
Wave. 93,700 yards of cable con-
nected.

Curve XVIII.— No Load E.M.F.
Wave. 71,200 yards of cable con-
nected.

Curve XIX.— E.M.F. wave. 51,800
yards of cable connected.

to obtain good results under these circumstances, for if resonance
be too pronounced the oscillograph motor stops, and the results
cannot be noted. I do not think that Curve XV. shows the conditions
of maximum resonance by any means; in fact, I have had instan-
taneous glimpses of alarming resonance, but for the reasons already
stated I could not reproduce them.

I used to think it a safe procedure when shutting down to gradually
slow up the main engine and let the voltage die down gradually;
similarly it was my opinion that one should excite the generator,
and run up slowly on the cables when starting up, but from these
experiments it is clear that by so doing one passes through the
conditions for maximum resonance with all odd harmonics above
the nth. Undoubtedly the better procedure is to run the machine
up to full speed, and then slowly to bring up the excitation to the
normal, and to reverse the procedure when shutting down.

670

FIELD: A STUDY OF THE PHENOMENON OF [Glasgow,

Curves XX. and XXI. more nearly approach to the E.M.F. curve
of the alternator on open circuit.

Another important point to consider is whether resonance due
to a higher harmonic can occur under load conditions. The curves
generally indicate that this is not so, the ripples being apparently
damped down to a minimum under load conditions.

Curve XXII., which was taken at half normal load, shows,
however, certain ripples accentuated, and the question is worth
inquiring into.

Look at Curve XXIII. We have already seen that the back
E.M.F. of the rotaries being a smooth curve, the higher current
harmonics in the system are wattless, and are either capacity or
self-induction currents. The current ripples which flow into the
rotaries, representing self-induction currents, no doubt partly
neutralise the capacity of the system, but at the high frequencies

srf

Curve XX.— No Load E.M.F. Wave.
9,150 yards of cable connected.

Curve XXI.- E.M.F. Wave. 2,290
yards of cable connected

Curve XXII.— Taken at substation
C as load falls off between 11-12 p.m.,
125 amps, at power-station.

Curve XXIII.— E.M.F. Wave
Rotaries on no load (normal excita-
tion), 20-30 amps, at power-station.

we are dealing with it is impossible that the whole capacity effect
can be thus neutralised, and we have at such frequencies as 275 and
325 cycles a balance of capacity effect left over ; it is then merely
a question of the number of rotaries, transformers, and cables in
service which decides whether or not partial resonance will occur
under load conditions.

In this connection it must be borne in mind that if r is the ratio
of transformation of the transformers (in the case in question r = 20),
a coefficient of self-induction in the low-tension side is equivalent to
r^ (= 400) times the coefficient of self-induction in the high-tension
side. When, again, we compare the capacity and self-induction
currents (for the same voltage applied) at a high frequency, such

1903.] RESONANCE IN ELECTRIC CIRCUITS. 671

as the 13th, and remember that the former varies directly, and the
latter inversely as the frequency; we see that even a large wattless
current in the low-tension side J due to self-induction at the funda-
mental frequency, can have but a small effect in neutralising the
capacity effect of the cables at the high frequency. This is easily
calculated out.

From the foregoing, it is evident that it should be easy in any
particular case to determine experimentally what conditions of
capacity, etc., will give maximum resonance.

For example, if we know the length (/) of cable which produces
resonance with the p^ harmonic, one generator only working, at the
speed s revolutions per minute, we know that the length which will give

resonance, with the ^'* harmonic at a speed s, will be / (^ ) ; again,

if two generators be thrown in parallel, we halve thereby the inductance
of the circuit, and therefore resonance with the same harmonic will
only occur with twice the amount of cable connected to the circuit.

This fact alone will usually prevent important resonance effects
under full-load conditions, the period of greatest importance from
this point of view being that of light load, where the cable system
is being fed from one generator which is perhaps of relatively small
proportions.

It must not be supposed that I attach great practical importance
to the above considerations of the possibility of the occurrence of
resonance; as a matter of fact, although in Glasgow, I was for a
long time unaware that anything of the kind could be going on, we
experienced no difficulty at all, and it is the general opinion of a
great many experienced engineers with whom I have spoken on
the subject that resonance is not to be generally feared in ordinary
well-laid-out systems.

I do J however, consider it important for each engineer, as far as
possible, to be conversant with the conditions under which resonance
is Ukely to occur in the system under his charge, and to avoid the
combination if it is at all likely to be serious.

It is further conceivable that slight resonance effects might occur
in cable circuits supplied by continuous-current machines. All such
dynamos have a ripple of a high order present in their E.M.F. In
the case of a rotary converter this ripple may, as we have seen,
be pronounced, and I think it possible that considerable resonance
effects might be found in such cases* It would be interesting to
look for them.

PART II.

The second part of this paper is descriptive of some experiments
I carried out to examine optically the ^ore temporary or non-periodic
effects in electric circuits, by which I mean such effects as the
growth of the current in a continuous- current circuit containing
self-induction, or the oscillatory nature of the charge current of a

672

FIELD: A STUDY OF THE PHENOMENON OF [Glasgow,

cable when switching it on to a direct- or alternating-current circuit,
and other similar effects. I am perfectly aware that these phenomena
are treated mathematically in the various text-books on the subject,
but I still think the experiments highly instructive.

In order to render these results visible on the desk of the
oscillograph, it was necessary to make them occur periodically and
synchronously with the motor of the oscillograph. I therefore con-
structed a contact maker, and attached it to the shaft of a disused
tramway " motor, which had already been provided with two slip
rings for other purposes. The motor was suppli^ with direct
current, the oscillograph motor connected to the slip-rings, and the
strips suitably connected to the contact maker. The latter consisted
of a continuous ring, and a second one cut into sixteen equal parts

FiG. i6a.

v\AAAAAAA^||4

Fig. i66.

with provision for connecting them up in any way desired. The
motor having four poles, I connected the contacts in four groups of
four, and used this arrangement throughout.

Figure i6 (a) and {b) shows my general arrangement.

In position (a) it will be seen that the charge current for the
combination of capacity and self-induction passes through the
oscillograph strip S ; in portion (6) the combination discharges
through S ; this process, occurring synchronously with the vibrations
of the oscillograph mirror, appears as a stationary curve and can be
photographed as heretofore. The photographs, which I here re-
produce, had an average of 30 seconds exposure.

Curve XXIV. represents an ordinary make and short-circuit without
self-induction or capacity.

1903.]

RESONANCE IN ELECTRIC CIRCUITS.

673

Curve XXV. represents ' the growth of the current in a circuit
containing a transformer on open circuit.

Curve XXVI. represents the above, but with half of the high-tension
^rinding short-circuited through a single lamp.

Curve XXVII. represents the same, but with the whole high-tension
vrinding short-circuited through the incandescent lamp.

The annihilation of the self-induction due to the short-circuited
secondary is noteworthy. I have used the curves thus photographed
for the determination of the coefficient of self-induction of a circuit ;

Curve XXIV.— R = 2425 ohms,
L = O. K = 0,'.R.P.M. = 750, V = 2-6
volts.

Curve XXV. — R = 244 ohms, L =
transformer H.T. open, K = O, R.P.M
= 760, V = 3-9 volts.

Curve XXVI.— Same as XXV., but Curve XXVII.— Same as XXV.,
with half H.T. winding short-cir- but with whole of H.T. winding
cuited. ^ short-circuited.

it will be noticed it gives the value of the coefi&cient of self-induction
for practically zero current, since the current through the oscillograph
should at no time exceed o'l ampere. As such, the method may
prove useful to others who have an osdilograph at their disposal, and
I will therefore illustrate it briefly.

Fig. 17.

We know that the law of curve from A to B, Fig. 17, is

y and x representing distances only, and being measured to the same
scale.

We have then that — -j-, - = — ^ ; in other words, if we measure
y for each value of x from the curve, and plot log^ y and x to the same
scale, we should obtain a straight line not passing through the origin,
and with a negative slope equal to p.

674 FIELD : A STUDY OF THE PHENOMENON OF [Glasgow,

But we know that px^=j /,* ; /, being the time occupied by the

discharge from A to B. . • . L in secohms =

pxXz

R being in ohms, and ti in seconds.

/, is of course easily determined by the speed of revolution of the
contact maker. In my experiments, /, was ^th second. It is to be
noticed that the constant of the oscillograph or deflection per ampere
does not enter in.

It may be urged that where y is very small it will not be possible
to measure it accurately. This is true ; the curve of discharge is really
asymptotic to the zero line, log 0 equals — oo , hence if we take the
zero line the smallest amount too high or too low we should get, on

Fig. i8.

Curve XXVIII.— Shaded Area
defines V during charge and
discharge.

plotting logarithms, curves either running out to infinity within a
finite time or becoming parallel to the zero line (see Fig. i8).

We can get over this difficulty in the following way. We know
y measured from the true zero is k^-^. Let us write y© measuring
from false zero as M -f A f-^, then

dx ~M + /fec-^* "" "" ^^0

that is measuring the slope of the logarithmic curve reckoned from the
. false zero line gives us an inaccurate result in the ratio of y to y© at the
point in question. It is clear then that the logarithmic curve will become
more and more nearly straight as it approaches the vertical axis of y, if
therefore it be produced and the slope measured at .this point we know

the error should not be more than ^ at the origin, which in my opinion

might easily be kept down to within i per cent.

If before drawing the logarithmic curve we multiply our log y

values by -A , then the slope will be such that if we mark off on the

vertical axis rs to represent R in ohms, s / will represent L in secohms.

• R

Yj / is a mere numeric ; the dimensions come out M® L** T°.

1903.]

RESONANCE IN ELECTRIC CIRCUITS.

675

Curves XXVIII. and XXIX. represent the way the potential rises
at the terminals of a self-induction shunted with a resistance greater
than its own when the circuit is ruptured ; the connections were
made as in Fig. 19, the curves
explain themselves. 1

The strip Sa being connected ^.—.^^^^^-VVVVVVVH
across the self-induction as shunt ^ ^ ^^^
really acts as a voltmeter.
AVhen the discharge takes place
the same current flows through
each strip, the rise of voltage

is therefore represented by ;.

0 6— Oa; Oa representing the Fig. 19.

voltage at the instant before

discharge. Of course, by making r large enough the potential across
the self-induction might be brought up to any value provided
the circuit be ruptured with absolute suddenness, i.e., no spark
occur at break, and there be no eddy currents induced anywhere by
the circuit. These conditions are, of course, impossible, but it is
well known that there is really no absolute limit to the rise of potential
on rupturing a circuit possessing self-induction.

We now come to the oscillatory charge and discharge currents
in circuits containing self-inductions and capacities. These experi-
ments were made as indicated in Fig. 16. and are represented in
Curves XXX.-XXXVI.

Curve XXIX.— Taken from Curve
XXV^III. ob-oa represents rise in
voltage on opening circuit.

Curve XXX.

Jf/\^s^^

■V--^

Curve XXXI.

Curve XXXII.

In the first series we start with capacity only ; the charge and
discharge are so rapid that the oscillograph apparently overshoots the
zero line.

The exponential term in this case is c"*^ In my experiments the
capacity was 1*5 x lo^ farads, and resistance roughly 25 ohms. The
maximum self-induction coefficient was approximately '33 secohm (it
was a variable self-induction dep>ending on tl^e current strength), the

676 FIELD : A STUDY OF THE PHENOMENON OF [Glasgow,

combination thereforefhad a natural frequency of about 225 cycles per

second.

I R •

We see then that ^^ = 2*67 x 10*, and y- = 75, that is the process

depicted in Curve XXV. as happening in 3'5th second, occurs in Curve
XXX. in TTTTnrth second. Under these circumstances the natural fre-
quency of the oscillograph strips will, of course, come into play.

Curves XXXI.-XXXIV. represent the oscillations in the self-same
circuit, as the self-induction is gradually increased. It is to be
noticed throughout that the resistance in circuit on discharge is
always less than that on "make.** An examination of Fig. 16 will
show that this is the case.

Curve XXXIII Curve XXXIV.

Curve XXXV. Curve XXXVI

Curves XXXV.-XXXVI. were taken with exactly the same apparatus^
with the exception of the self-induction. Here a different transformer
was used. I reproduce them on account of the irregularities at
"make" and discharge. I cannot quite account for this. I certainly
had some leakage effects going on in the circuit, but they did not
seem able to account for this initial irregularity. There was another
abnormality which I noticed on closing the circuit ; there was an
instantaneous oscillatory curve depicted very much larger than the
permanent ones. It was merely instantaneous. This, again, may
have been a charge leaking into the condenser in some way, but
I had no time to investigate it fully. Perhaps the mathematicians will
tell me if some other effect is possible, and, if so, it would be well
worth while to try and repeat it, and investigate the matter further.

Curves XXXI.-XXXVI. show distinctly how rises of potential occur
on switching cables cither on to direct- or alternating-current machines.

The curves themselves are curves of current, but we know that
the curve of E.M.F. across the condenser is of the same shape but
displaced in phase, the maximum of E.M.F. occurring when the
current is zero.

In this case it is easy to see that the maximum voltage across the
condenser will reach nearly twice the steady value, thus : —

'At the moment of closing the switch the current is zero, therefor^
the ohmic drop is zero.

1903]

RESONANCE IN ELECTRIC CIRCUITS.

677

The charge in the condenser being zero, v is likewise zero (see
Fig. 20). The supply EIM.F. V must therefore be counterbalanced by
a back E.M.F. in the self-induction due to the growth of the magnetic
flux.

Now the voltage across the self-induction is (V — r), but since

C = K -— , and at zero time C = O, we have at the moment of closing
the switch the voltage across the self-induction or V — r = V and

o ; this means that this voltage starts at its maximum

value, viz., V. If we subtract V and reverse, we get the voltage across
the condenser or v. The oscillations of v and c are shown in Fig. 21.

We see then at an instant after the start or at the end of the time of
one-half oscillation the voltage v has risen up to nearly twice V. The
voltage across the cable therefore oscillates about the constant value V,
and finally settles down to that steady value. As there are a number
of important particular cases where such oscillations arise in general
practice, I will here state a few using a minimum of mathematical
symbols.

■0001)0000000"00"0">

:/f

Fig. 20.

The differential equation which holds for case in Fig. 20 is of the
familiar form —

d'v
dt^'

R dv .V

"^ TTdt "^ LK

(15)

Now, in the cases we are about to consider, V may have a constant
value, and the equation applies to the charge portion of curves XXXI.~
XXXIV. ; V may be zero, as in the case of the discharge portions of
the same curves ; or V may be a sine function of the time, or

Vo sin 2 IT « /.
In the first case we know the general expression

v=zV -h A€

satisfies equation (15).

I = R'

If, however, t-jt is <: -y^ the discharge is no longer oscillatory

and we shall not consider these cases.

A and f are constants depending on the particular conditions of the
problem which must be fulfilled.

If V is zero, the solution (16) may still be applied.

678 FIELD: A STUDY OF THE PHENOMENON OF [Glasgow,

If V ^ Vo sin 2 IT « /, we know that the final state at which the
voltage V will arrive will likewise be a sine function. We can write
down this final state as

Vosm2irnt , s

Where 0* represents the operator -ri ; we will express this function

as V = vq sin (2 it «/ 4- 0*)«

A general solution which will be applicable to the initial as well as
the final state of things will therefore be —

V = Vb sin (2 irn / + 0^ + Ac"" ' sin | \/{i^^^ - \^ ' + 0) (18)

d V
The current, or K -v^ will in this case be represented by the expres-
sion—

C = 2 IT « Kt-o cos (2 IT fi/ + 0*) + — /^— «

Vlk

'^"^ { A^-^) ' + . + tan - V^-^^ } (>8«)

The first expression representing the final state, and the latter the
initial disturbance.

We shall have occasion to make use of this result later.

We will now, however, make a small digression, and briefly examine
the nature of the oscillation represented by —

V = A'c"" sin jS / ( where a = ?-
1 2 L

I and

We will take the case where the voltage across the condenser
follows this law.

The coefficient A will, in lieu of a better term, be called the co-
efficient of the oscillation, v will be zero when fi tz=z nw, or when

' = -g^ ; " being any integer. The successive zero values, therefore

occur after equal intervals of time, viz., ^.

The maxima will occur when -— =s 0;

(it

Hence the maxima occur when

/3
* See P6rry's " Calculus for Engineers."

1903.] RESONANCE IN ELECTRIC CIRCUITS. 679

This shows that the successive maxima occur after equal intervals

of time, viz., ^, but they do not necessarily occur exactly in the middle

of the time-interval between the two successive zero values. Since the

current through the condenser = K ^ , it is clear that the zero values

of the current occur simultaneously with the maximum values of the
voltage across the condenser.

if V

The maximum values of the current occur when ^^ =z o, or when

JL^ e"°' (sin /3/ - 2 tan-' ^)^o
L K \ a/

n n
i.e,y when / =

n v 4- 2 tan-"* ^^

The current maxima therefore do not necessarily occur simul-
taneously with the zero values of v.

R« 1

If, however, -j^ niay be neglected in comparison with -t— j-,

tan- - = ::
a 2

and we can represent the current by the expression —

AK -«/

Vlk*

cos j3 /,

in which case the maxima occur half-way between the zero values,

and the current maxima occur simultaneously with the zero values

of V,

_^/
Further, in this case and with the oscillation At ^^ sin ^t the

absolute maximum occurs after time — ^, the value being —

AT ^ T— »
C 4 L

and in the case of the oscillation A c" ' *- cos )3 /, the absolute maximum
will be equal to the coefficient of the oscillation, viz., A, i.^., the oscilla-
tion starts at its absolute maximum.*

• The oscillation represented by v = A«~ " ' cos f /3 ^ - tan ^ J has zero

slope f or -rj — 0] when / = o. This is the true form of the oscillation

/3 R'

which starts at a maximum value, viz., A -,--—.. -. Where, however, -— -

Ja^ -\- (^ 4 L'

may be neglected tan-* — = o, and the maximum or initial value is A.
Vol. 82. 45

680 FIELD: A STUDY OF THE PHENOMENON OF [Glasgow,

In the cases we shall consider here - r^ is negligible with regard to

I ^

— 1^, so that we may apply the above simplifications, and write as the

frequency of oscillation —

J /J

2 7r^ Lk

There are two rules which it is of importance to keep in mind on
account of their bearing on the voltage and current rises in alternating-
current circuits when oscillations arc started. They are as follows : —

(i) If in a circuit consisting of a capacity and a self-induction a
voltage oscillation be started of which the initial maximum value is «^
the coefficient of the current oscillation will be —

CoV^

Lie

2irn

where Co is the maximum value of the condenser current after the
steady state has been reached if the voltage Vq sin 2 tt nt is applied at
its terminals.

(2) If a current oscillation be started of which the initial maximum
value is Co, the coefficient of the corresponding voltage oscillation will
be—

^v/lTc

where vo is the maximum value of the voltage wave which must be
applied to the terminals of the self-induction in order that the current,
after the steady state has been reached, may be of the shape Co sin
2irnL

2Trn

represents, of course, the ratio of the frequency of the oscillation to the
frequency of the supply circuit. These rules are the obvious outcome
of what has preceded.

We will now return to the treatment of the case where, say, a cable
is switched on to a D.C. generator which possesses self-induction, v is
represented by equation (16).

At time / = 0 we have to satisfy the conditions rz=o and- - = o

or C = o.

The first of these conditions results in the equation V = — A sin ^,
and the second shows us that at time o the oscillation starts at maxi>
mum or crest.

The frequency of oscillition will be —

1903.] RESONANCE IN ELECTRIC CIRCUITS. 681

the time occupied by a half oscillation will be —

^ LK""4L»

. at time / =

^ L K "" 4 L"

i' = V + A« "■'" "■-• sin (« + ,r)

= v(i4-e ^/lik-l) . (19)

and this will be the maximum value to which the E.M.F. across the
cable can rise.

At the limit ^^-j^ = i, which is the limit at which the current ceases

to be oscillatory, v^V and there is no rise of voltage.

We cannot take a negative value for the >/ terra in equation (19),
for taking the negative value of the square root gives a result for some-
thing that was happening before we began to count time. It has
no meaning except in the case of an oscillation having been started,
and the zero of time being taken at some period subsequently.

We can therefore dismiss this case. The value of the exponential
in (19) must therefore be between i and o. We have discussed the

latter condition. The former is attained when -^^ =s 00. Therefore

when R or K is very small, or when L is very large, v will rise to a
maximum of practically twice V.

It is interesting to think of the case where a voltage V is suddenly
applied to one end of a coil of large self-induction and low resistance,
the other end being free. The interruption in the circuit is equivalent
to a very minute capacity. An extremely rapid oscillation will then be
set up through the coil, and the potential at the free end will oscillate
about a mean V with an extremely high frequency, the oscillation
continuing for an appreciable time. ,We are now getting into the
range of the wireless telegraphist. In the case of a cable being
switched on to an alternator we may apply the self- same result if
the circuit be closed at the maximum of the E.M.F. wave, and this be
sufi&ciently flat or the oscillation sufficiently rapid for us to assume that
there is no appreciable diminution of the E.M.F. during the time of
one-half oscillation. In this case we may say the maximum voltage
will be nearly twice V, and under other conditions less.

If the cable be already charged and have a potential difference at its
terminals of —V, and be switched on to a circuit of P.D. -f V, the
maximum to which it can be subjected will be nearly 3 V.

It will be seen at once in the case of a steady voltage V, and it can
be shown to be equally true in any other case, that provided R is small
in comparison with 2 tt w L in Fig. 20, the voltage across L due to the

682 FIELD : A STUDY OF THE PHENOMENON OF [Glasgow,

oscillation is at every instant equal and opposite to v, hence we have the
same condition as that for resonance during the steady state, viz., that
a current flowing through a self-induction in series with a capacity
produced a P.D. across the former equal to that across the latter,
but opposed in direction. In these initial stages we are therefore also
dealing with resonance efiFects, the difference between that, where
we have a steady state of resonance, we have to adjust L and K so that

— • i Y~i> corresponds to the frequency of the supply circuit.

During the unsteady state we have resonance with any values of L and
K, for given an initial pulse of E.M.F. or current, the frequency of

oscillation (w,) will be self-adjusting so that still 2irn, ^ TTl?* ^^

^ L* l\.

the circuit in Fig. 20 be closed when the E.M.F. is zero, the steady state
is not instantly reached, for this would imply that the current into the
cable was very nearly at its maximum value, but we know that it will
be zero. We have therefore to consider the expotential term in equa-
tion (18).

The conditions we have to satisfy arc, at time

/ = 0 V = 0

T^ = 0 and ^ = 0
a I

C = 0

The first condition is already satisfied where V = V© sin 2 r » /.

The second involves vo sin 0* -f- A sin ^ = 0 (20)

The third involves —

A K ( / \ )

2 9r « K z^o cos 0» -f -JyIc ^°s ] ^ + ^^""^ (~) [ ~ ^ • ^^^)

These conditions merely state that the initial value of the voltage and
current oscillation are equal and opposite to the values of voltage and
current which exist after the steady state has been reached at the
moment of the E.M.F. wave when V passes through the zero.

We can of course solve equations (20) and (21), and obtain A and f
in terms of vo and 0' which again are determinable from equation (17).

But in the case under consideration we can cut this short in the
following manner : — We know that the P.D. across the self-induction
(which is the self-induction of the generator) is practically directly
in line with V, in other words 0' = 0, and therefore also 0 = 0. There
is still another condition which must be true at time / = 0. We know
that at every instant the P.D. across the self-induction = V — v, but
(V — 2^) may be expressed as : —

at time / = 0 this is also zero, and therefore if R is small in comparison

dt'

with L (which is the case with every alternator) we may say -t-7 ^ 0 at

zero time.

This last condition shows us that at the mpii[ient of starting, the

190S.]

RESONANCE IN ELECTRIC CIRCUITS.

688

current oscillation has its maximum value, which is equal and opposite
io2irnKvo. We may therefore say at once that the coefficient of the
oscillatory voltage is —

2 IT ti

This will be a very small oscillation which starts when vo is zero ;
the rise of voltage across the cable will therefore be very small if
switched in at the moment of zero E.M.F., but there will be a current
oscillation of which the initial value equals the maximum value
after the steady state has been reached.

I do not propose to lengthen out this inquiry by going into other
more complicated cases, such as switching on cables with transformers
connected across the ends, or switching on circuits to generators
already loaded on other circuits, since in no case are greater rises

Fig. 21.

of potential called into existence by initial disturbances than those we
have already considered.

I will therefore take up the special case of switching off a cable
circuit already loaded with a highly inductive circuit, such as lightly
loaded transformers, or worse still, a circuit opening on the high-
tension side, the low-tension circuit being loaded on an inductive
load.

Two limiting cases are those of special interest — (i) When the
circuit is broken at the moment the current is passing through zero ;
(2) when the circuit is broken at the instant the current is at its
maximum.

Dealing first with the case of a bank of transformers, the secondary
of which is on open circuit.

Let the maximum of the charging current of the cable be Cg and of
the transformers C^, then we have the relations —

Cjj = 4 TT* w' L K Cl and 2 tt n L C^ = Vo

If the circuit be opened at the moment the current Cj^ and C^ are

684 FIELD: A STUDY OF THE PHENOMENON OF [Glasgow,

zero, the voltage being vo or the maximum of the steady state, it is clear
that there will be excited a voltage oscillation starting with a maximum

value of Vo. The coefficient of the current oscillation will

^^ Vt*^'

that is to say, the coefficient is to C^ in the ratio of the frequency of
oscillation to n ; and to Cl in the inverse ratio. There will, however,
be no rise of voltage.

If the circuit be opened when Cl and Cg are at their maximum
values, or when the voltage is zero, a current oscillation will be excited
starting with the maximum value C^.

The coefficient of the voltage oscillation will then be y/h Cl, that

is to say, the coefficient is to vo in the ratio of the frequency of
oscillation to the frequency «. This will, of course, usually result
in a considerable rise of potential. If the secondary, however, be
not an open circuit, it may act more or less as a short-circuited
turn and either damp down the violence of the oscillation if the
secondary circuit be non-inductive, or increase the violence of the
same if the load be very inductive. In any case the eflFect of the

Fig. 22.

secondary may be represented by a shunt circuit in the primary, thus
in Fig. 22, /j represents a choke coil having the same self-induction
coefficient (Z,) as the primary circuit of .the transformer on no load.
R, La represent the resistance or self-induction, as the case may be,
which, when connected in parallel with /, will behave, as far as the
supply circuit is concerned, as does the transformer on load. If
the transformer supplied motors, it would be necessary to include
in the shunt circuit a back E.M.F. Taking the worst case, where the
secondary circuit is loaded inductively at the moment of interrupting ;
it is clear that during the oscillation that follows the total energy
of the system will be at one instant stored electro-magnetically in the
magnetic field interlinked with the circuit, at another electro-statically
in the capacity.

The total energy at the moment of interrupting is

the first term representing the total energy stored in the capacity
in watt-seconds at the moment of interrupting, K being tne capacity and
V the voltage at the terminals at the moment in question ; the second
term being the watt-seconds stored in the transformer due to its

1903.]

RESONANCE IN ELECTRIC CIRCUITS.

685

magnetic state, C, C, being the primary and secondary current at the
moment of interrupting, and <r, (r, the number of turns of primary and
secondary respectively; while the last term represents the energy
stored electro-magnetically in the secondary external circuit ; L being
coefficient of self-induction of this external circuit. *

The maximum value of the voltage oscillation will be slightly less
than V, where

This, of course, is readily calculable; it will represent a very con-
siderable and usually a highly destructive rise of potential.

As a last example of the kind, we will consider the oscillation
in a circuit consisting of a capacity and self-induction, where at
the moment of the interruption
the voltage across the capacity
is — r„ and the current flowing
through the self-induction is C,.

We can consider the voltage
oscillation as the resultant of
two components, the first given
by the conditions whep / = o,
p = o, C = C„ the second given
by the conditions when / = <?,
r = — r„ 0 = 0. It is clear
that the sum of these oscilla-
tions will satisfy the fundamental equation, and the initial conditions,
viz., when / = o, v = — v„ C = C,.

We have, however, already considered both components separately,
and can write down the oscillations forthwith in their approximate
forms, as ; —

. = - .. rr.' COS (yj^) / + C. yC ,- A' ,,, (yii) ,

C = r. ^l rr.' sin (^^j l + C. r-V cos (^/J^) ,
or —

I could ha^e obtained these results by means of the oscillograph
had I thought my capacities would have stood the severe strain.
The connections would have been as in Kig. 23. The current curve

Fig. 23.

686 FIELD : A STUDY OF THE PHENOMENON OF [Glasgow,

through S would then be of the nature shown in Fig. 24. If we make
the resistance in the battery circuit one-half that in the condenser

circuit, we have the exponential
terms during both charge and
discharge operations the same ;
in other words, the curve
representing the oscillation
will be found to just fit into
the cone formed by taking two
of the curves ABC, repre-
senting the charge period.
This is shown dotted in the
diagram.

A few words with regard
to the frequency of oscillation
of which we have been speak-
ing.

A 5, 000- volt cable of such
length as to give i microfarad
capacity connected to a trans-
former of which the .magnet-
ising current was i ampere
at 50 CkJ, or with an L of
15*9 sccohms, would resonate

2 IT V 15*9

with a frequency . ,

or 40 cycles per second. A
generator on the other hand
which would give a short-
circuit current of 200 amperes,

or with an L of ^5^ secohms
200

would produce an oscillation of

frequency of 40 x ^200 = 560.

In large systems the oscillations

produced on switching on

cables to their generator will

usually be of a much higher

order than those produced in

the system on switching ofiF.

PART III.

We have up to the present assumed that, provided the 3-phase
system be symmetrical, the capacity effect of the cables may be
exactly reproduced by substituting in place of the cables conductors
without capacity, but with a single combination of capacities

1903.] RESONANCE IN ^ELECTRIC CIRCUITS. 687

connected between Ihem and earth, as represented in Fig. 14. We
know, however, that this is not strictly true ; a 3-core cable really
can only be represented by a distributed capacity, as in Fig. 25,
where ABC represent the 3 cores, and the dotted line an imaginary
earthed conductor of zero resistance. Now, if in this case an E.M.F.
be suddenly applied at one end of the cable, the other being open-
circuited, the whole cable does not become instantly charged; uc,
the current at the point px in core A will have a difiEerent value
from that at point ^ at every instant. Further, the potential at ^,
above earth will not be the same as that at /►,» and the quantity of
electricity charging the cable per cm. length at p^ will be different
from that at ^a.

On the other hand a definite and appreciable time will be necessar}'
for the charge to be felt
aU along the cable. A x J,J- J-X-L JLXX J-J-O,

We have, in fact, the £. J.J.J.J. J. J.^.J. J^.j:.^

same sort of problem as « -r-r-rnr"rT"r~rTT"rT |
that of sending signals J*

through the Atlantic ^'^"X'X'X'X'XXUrXiru:"

cable, where, if a pulse ^
of E.M.F. or current be
injected into the cable

at one end, an appreci- ^^' ^^

able time is required
before the pulse is
manifested at the far
end.

What goes on may
be briefly sUted to be as ^^®- 2^-

follows : —

If at any instant the potential at i (Fig. 26) is zero, and current
is flowing from 2 to i, the potential at 2 will be positive, which means
that the capacity K must have a definite charge while that of *, is
zero.

Again, if current is flowing from 5 to 4 to 3 to 2, the potential at 5 will
be higher than 4, of 4 than 3, of 3 than 2 ; hence the charge in ^5 is greater
than that in ^4 ; of ^4 than k^ ; of ^3 than K- Now every capacity takes an
appreciable time to charge, and, therefore, there will be a time-growth
of charge along the cable, *, arriving at its full charge last.

Now let us assume that by the time ^, has received a definite charge
the potential at the sending end has been gradually reduced to zero ;
the charge in the initial capacity will then be zero, and in the
final capacity k^ a maximum. We have then the exact reverse of
the initial state when the charge in k^ was a maximum and in k, zero.
There will now be a return current tending to equilibriate the
potential along the conductor. This return or reflected wave will
require a definite time interval to reach the sending end, and if the
applied E.M.F. at the sending end is periodic, and the returning
waves synchronise with the applied periodic E.M.F., a state of
resonance will be set up. This might reach dangerous proportions,

h 7 9 € ^ 3 9 1

JL^ fr Yi V€ K y^i ^9 Wf.

^^^AA^A^f^^A^f^

688 FIELD : A STUDY OF THE PHENOMENON OF [Glasgow,

a small E.M.F. at the sending end involving an extremely high P.D.
at the far end.

I have worked out this case for a 3-core cable, with an impressed
E.M.F. at one end, consisting of a fundamental of 25 cycles and a
13th harmonic; but find that the length of cable required before
a dangerous state of resonance is set up is far beyond anything
at present in use in this country for power transmission purposes.
I do not propose to give the full mathematical details of this problem
as they may be found elsewhere.

As, however, this particular case of the general problem is inter-
esting to electrical engineers, I propose to apply here the solution
of the same to a practical case.

We will confine our attention to a 3-core lead-sheathed high-
tension cable ; area per core = '2 D"

Let p = resistance of i core per mile = '22 ohm.

Let K = equivalent capacity per leg per mile (see Fig. i2^) =
•5 X 10-* farads.

Let X* = coefficient of self-induction per core per mile {i.e,, X is a

coefficient such that volts drop in each core per mile = p c -h X ^.j.

Let c be the current at any point and at any time, flowing axially
along the conductor under consideration.

Let V be the potential above earth at a similar point.

Fig. 27.

We need only consider one core, and may think of it as consisting
of a conductor as represented in Fig. 27.

The cable is on open circuit at the far end ; at the near end a sine
wave of E.M.F. is applied.

The fundamental differential equations of the problem are : —

_ =p._ + X._ (22)

__=p«._ +X._._ (23)

^^ = -«^v-; (24)

dx d t

♦ I here represent resistance, coefficient of self-induction, and capacity
per unit length, by Greek letters, as these quantities are of different dimensions

from the R L K previously employed ; we saw that ^J :^ was of the
dimensions of a frequency or /- , we soon shall see that ^/ ^- represents a

velocity or --^— . It is of importance, in order to avoid a confusion of ideas,
to keep this point well in mind.

1903.] RESONANCE IN ELECTRIC CIRCUITS. 689

A solution for v is —

» = Vo €** sin (2 IT » / + a x)f
and for current —

c = Co €** sin (2 IT w / H- a 4? + i//).

These solutions would apply to the case of a cable infinitely long ;
we have, however, to satisfy the terminal conditions —

when 4: = <?, V = Vo sin 2 irn /,
when x = lfCsso,

I being the length of the cable in miles.

The particular solutions which satisfy these terminal conditions
are: —

V = Vx €~** sin (2 ir n / — a x + <^) +

V, e-M^-*) sin (2 IT n / — a (2 / — jr) + ^)

_ 2xnicV, 1^"'* sin (2 IT « / — a ;r + ^ + e) — l

^ ~ Va,"+ a,»(e-«(»/-*) sin (2 irn / — a (2 / — ^) + ^ + «))
where a = Vtt n k (I — 2 ir » X)
a = J'/r n K {I -|- 2 Trn X)
1= ^» + 4 ^ «' X»
V — ^^

^« ^ -4a/ —2a/

/ —4a/ —2a/

i^ I + € + 2 * cos 2 a I

tane =-

-J a/

c sin 2 o /
tan ^ = zri^,

I 4- € cos 2 a I

An examination of the form of the solution of v and c shows that
each consists of an original plus a reflected wave. If the cable had
a length of 2 /, then the first term gives the value of the original
wave at, say, the point />, ; the second the value of the same wave
at point Pa (Fig. 28), and the solution tells us that in the case of the
cable of length /, the actual value of the wave at p^ is in the case
of the E.M.F. the sum of the value at pi and />, at every instant ;
in the case of the current the actual wave at />, is the difference
between the values at p^ and /►a.

It will be noticed that the differential equations (22), (23), (24),
which obtain for the case in question involve three conditions : —

(ist) If we consider any particular short portion of a given cable
such as a 6, the quantity of electricity entering this portion axially
at a in a given time is equal to the quantity leaving axially at 6, plus the
accumulation of electricity at the side walls bounding the portion a b.

690 FIELD: A STUDY OF THE PHENOMENON OF [Glasgow,

(2nd) The accumulation of electricity as above is equal to the
pressure obtaining at the portion of the cable a b, multiplied by a
constant depending on the nature of the containing walls, and not
on the conductor. If this constant is zero there can be no accumula-
tion, and the quantity entering a equals the quantity leaving at b.
The above, which merely state the electrical conditions, are obviously
those for an incompressible fluid flowing through a pipe with
elastic side-walls. For if the side-walls be rigid there can be no
accumulation in any portion of the tube; if elastic, the quantity
entering any cross-section such as a equals that leaving another
cross-section 6, plus the accumulation in the portion a 6, this
accumulation taking place in virtue of the elasticity of the side-walls,
and not being due to any compressibility of the fluid itself.

The 3rd condition is that the potential gradient at any moment
and at any cross-section is the sum of two factors — the first propor-
tional to the quantity per second passing the cross-section at . that

2l'C0

-ac —

nr -At ff ^1, fM ^^

— ^

** Y ^ * y •!*

A. J , Ax,

^"■""

^"^ '

t^G. 28.

moment, and second proportional to the quantity per second per
second or the acceleration.*

This last condition would similarly hold for a fluid possessing
inertia, and being retarded in its passage by true fluid friction (f.^.,
loss of head oc velocity). Now all these three conditions will very
nearly obtain in the case of water flowing through an indiarubber
tube. This is a most useful analogy to fix our ideas of what goes
on in a cable. (It will be noticed that the stnalogy of an organ pipe
which has been proposed is quite inaccurate, for in this case we
should be dealing with a compressible fluid in a pipe with rigid
containing walls.) I should like to see a model made consisting of a
suitable elastic tube with a blind end in which was included a small
reciprocating pump. In this way we should be able to follow the
propagation and reflection of the waves, also the propagation of
individual wave fronts, a most important point which we shall touch
on later. It is to be observed that the hydrostatic pressure at any
portion of the tube corresponds to the electric potential at any
portion of the cable, while the velocity of the fluid corresponds to
the current strength.

We shall obtain maximum resonance when a / = - : or when / =r — •

2 2a

The equation representing this in the electrical case will be

1903.] RESONANCE IN ELECTRIC CIRCUITS. 691

In this case the E.M.F. at the sending end will be of effective value Vo ;
and at the receiving end —

- - tan ^
2 6 ^ Y

Vl +€~"

— 2c

or -HI'—- .

I — f—irUn0

We will apply these conclusions to the case of a 50 cycle circuit,
containing a 13th harmonic or where n = 650 CXJ X can be calculatejd
from the formula —

X=(log, ^ + i) 10-^x3-22

where b = distance between cores, a = radius of each core.

Let us take a = '275 a" 6 = '8", then X per core per mile =z -000502
secohm.

If we say roughly that at this frequency 2 irnX ^ 10 p

. ^ /I— 2 7r«X i-^^^..^^

tan 6*

and ?-?-^ = 127.

I — €

It follows then that 13th harmonic will be magnified 127 times at
the end of the cable.

Putting in the at)ove values of p, c, and X in the expression ~ we

have / =s 23*5 miles.

It appears, therefore, it is quite within the region of possibility
for this class of resonance to occur on a system of moderate frequency,
supplying very long cables, and with slotted armatures containing
two or more slots per pole per phase. This case, though of importance

• This formula gives half the value of the self-induction of a circuit made
up of two parallel wires. In the 3-phase case the current in core i is at
every instant equal to the sum of the currents in 2 and 3. Now, the effects
of the currents in 2 and 3 on i will be independent of their relative positions,
provided their radial distance from i is not changed — we can therefore
consider them coincident, and calculate the effect on i as in the single-phase
case. We may consequently take the self-induction of a loop with the
same current per line as in i, halve it and consider this the E.M.F. of
self-induction acting in each of the line wires i, 2, and 3 at right angles to
the currents in those line wires. It is interesting to note that this formula
will give the same result per line wire as if we calculate the self-induction
of the inner of a concentric cable, the inner being of the same diameter
as each core in the 3-phase cable, and the radius of the outer being the
same as the distance between centres of the three individual cores, provided
this dimension is large in comparison with the radial thickness of the outer
conductor.

692 FIELD : A STUDY OF THE PHENOMENON OF [Glasgow,

in electrical engineering, and deserving of careful consideration, need
not necessarily cause uneasiness.

The value of the P.D. due to the harmonic at any intermediate
point of the cable will lie between V^, and 127 V^.

It is well known that the capacity effect of these long cables can
be imitated almost perfectly by connecting up a number of smaller
capacities with wire containing resistance and self-induction, and I
suggest it would be a subject of vast interest if some one would
investigate this matter experimentally rather than mathematically.

It is to be noted that since — is the wave length of the space wave

2 IT tt

in the cable, the velocity of propagation is ; when dealing with

such high frequencies that we can a£Eord to neglect p,a = 2irn ^ \k,
and the velocity of propagation becomes v -^ miles per second.

If X = 5 X io-<, and c = -5 X 10-* ; V x~ "^ 63,200 miles per

second, or approximately J the velocity of light.

There is still an important aspect of the subject of High Potential
Rises in circuits containing distributed capacity, self-induction, and
resistance (and every circuit does to a greater or less extent) which
I have not touched upon. I refer to the initial disturbances in such
circuits when the potential at any one point is suddenly altered.
The subject is a very difficult one to treat mathematically in at all
a general manner ; it must therefore be experimentally investigated.
I doubt even if the oscillograph will be of much aid here on account
of the extreme rapidity with which the phenomena take place.

A most interesting paper on the subject, entitled " Static Strains
in High-Tension Circuits and the Protection of Apparatus," was
read by Mr. Percy H. Thomas before the American Institute of
Electrical Engineers, 14th February, 1902, which is well worth study
by all who are interested in the subject. I am under the impression
(I hope I am mistaken) that the Proceedings of the American Institute
of Electrical Engineers are not read on this side with the attention
they deserve, and I will ask pardon for briefly explaining here the
nature of the so-called " Static Strains" of which the above-referred-to
paper treats.

In Fig. 29, S represents a source of high potential (V). A B, a
circuit or line of any nature at zero potential.

At the instant before closing the switch, the potential is represented
by the full black line in Fig. 30. Now on closing the switch the
line A B cannot, as we have seen, be instantly raised to the potential
V; in fact, at the moment of closing, the potential (assuming no
spark occurs) all along the circuit would likewise be represented by
the full line in Fig. 30. Instantly, however, the charge in the portion
of the system S T begins to distribute itself over the whole system
from S to B, the first effect being a tendency for the electro-static
charges in the neighbourhood of the switch to equalise themselves,
resulting in a moderation of the steepness of the potential line, as
shown dotted in Fig. 30.

1903.] RESONANCE IN ELECTRIC CIRCUITS. 693

This potential " front " will then travel along the system to B, be-
coming modified as it proceeds, depending on the constants of the line
and circuit. The question is, what is the potential gradient at all parts
of the circuit as this potential " front " reaches them ? It is a question
of vast moment. Every one who has worked much with high-tension
motors and transformers will have experienced difficulty owing to the
short-circuiting of turns and layers in a most curious way. I have seen
the winding stripped off high-tension motors, the insulation of which

Fig. 29.

was punctured with innumerable pinholes. The normal voltage be-
tween turns is a perfectly definite quantity, and accounts in no way for
the puncturing. But it is clear that if a potential front with a steep
potential gradient traverses the winding,the potential difference between
neighbouring windings or layers may be very excessive in comparison
with that after the normal steady state has been reached. For example,
if the distance a in Fig. 30 represents the length of two layers, it would
be possible to have momentarily the full potential of the circuit across
these layers.

On switching a high-tension motor on to a circuit, both poles cannot
be closed simultaneously. On closing the first pole we have the state
of things already discussed and represented in Fig. 30. The potential
front on reaching the dead end of the circuit is reflected back, there

.1...

Fig. 30.

occurs, one may almost say, a ** splash " of potential, possibly analogous
to the splash caused by a sea wave on reaching a boundary wall, and
similar to the reflected waves we have already discussed.

The same thing will occur on closing the second pole of the circuit,
only in this case the height of the potential front will be twice what it
was in the preceding case.

It is, of course, difficult to say whether the strain on the insulation
is greater in this case than in the preceding ; in general, we may say
that if the front extends over a distance of more than two layers of the
winding, the strain will be determined by the potential gradient.

These potential fronts may be created at any point of the circuit by
suddenly altering the potential at that point, eg., by short-circuiting
grounding, and the like.-

694 FIELD: THE PHENOMENON OF RESONANCE. [Glasgow,

This is a subject that will amply repay any one who will undertake
a careful research.

In conclusion I should like to state how very powerful a weapon in
experimental research Mr. Duddell's oscillograph should prove. There
are a vast number of investigations, of which the above are but unhappy
samples, which would amply repay any experimenter to carry out. It
is only given to mathematicians to see clearly with the mind's eye the
full physical interpretations of their symbols ; to ordinary engineers,
such as myself, who make no pretensions to wielding the mathematical
weapons, an optical investigation of such phenomena brings home in a
clearer way than pages of mathematics what is really going on. I
would suggest that the study of the effect of an arc on opening a high-
tension circuit, what goes on in sparks, in so-called liquid capacities
such as are used for starting single-phase motors, determining the
hysteresis loops of transformer circuits from the load current and
voltage curves, and a number of other equally interesting and instructive
series of experiments which suggest themselves at once, would form
the ground-work for most delightful papers.

These subjects are, moreover, of the greatest commercial import-
ance. Take, for example, the breaking of a high-tension cable circuit
in air or in oil, and trace out the rises of potential in the two cases. At
first sight one would think the air-break would be best ; it is not so, but
quite the reverse. What effect has the air arc then on the circuit ?

I wish now to acknowledge the very considerable help my former
assistant, Mr. S. Blackley, has rendered me in connection with the
oscillograms here reproduced. It has meant many a night till 2 or 3
a.m., when after a hard da/s work he has given up his spare time and
devoted himself to the work with the spirit of an enthusiast. I wish
also to express my indebtedness to Dr. Magnus Maclean for the help he
has given me in the preparation of this paper.

Professor Professor Magnus Maclean* wished to compliment Mr. Field on

MacEai. the excellence of his paper submitted, both from an experimental
and mathematical point of view. It was a paper with which he was
more or less familiar, as Mr. Field was kind enough to show him
many of the experiments some time ago, and the theories put forward
and the inferences deduced were mutually discussed on several occa-
sions. There were many points in the paper to which he would like to
refer, but, as the evening was far advanced, he would confine himself to
the investigation which Mr. Field gave to prove that the nth and 13th
harmonics are the most important.* The way in which he showed that
an nth and a 13th could be inferred from the 12 ripples observed in
the direct-current voltage was most ingenious, original, and, he thought,
correct.

But he did not think that Mr. Field was justified in stating as he did

• It would be more in accordance with ordinary notation and nomenclature
to call the term containing a frequency eleven times the fundamental fre-
quency the loth harmonic, and to call the term containing a frequency
thirteen times the fundamental frequency the 12th harmonic. Thus with
frequencies i, 2, 3, 4, . . etc., 2 is the first harmonic, 3 the second
harmonic, . . . etc.

1903.] DISCUSSION. 695

that these harmonics are the most important. As a matter of fact, the Professor
mathematical equation from which he deduced this result was an M^San.
assumed equation : and if one assumed a corresponding equation like
a (i -cos 6 kf), it would follow by the same reasoning and the same
nomenclature that the 5th and the 7th frequencies would be the most
unportant. To find by the usual analysis whether lower harmonics
were present or not. Professor Maclean got Mr. Blackley to magnify
four of the curves by means of a pantagraph. These magnified curves
were not very accurate, especially at the ripples, which were much
sharper than they should be. This was due, as Mr. Blackley explained
to him, to a sticking of the pantagraph. However, he thought they
were accurate enough to enable him to find if there were terms contain-
ing 3 or 5 times the fundamental frequency. The enlarged curves were
XV, XVII, XX, and another not given in the paper, but similar to XXI.
He would call it XXI. He only had time to try the last three mentioned
curves, and these only for frequencies 3, 5, and 11 times the funda-
mental. As terms containing even multiples of the fundamental
frequency cannot appear in these curves, the general equation is : —

/•(E) = E. sin ^/ + E3 sin (3 /^/ + ^3) + E5 sin (5/^/ + e^) -j- . . .
. . . -h E„sin(ii^/ + e„) + E,3 sin (13 /► / -f e.3) + . . .

The process of finding E, E3 E5 . . . etc. is well known. It simply
consists for finding Ejin dividing the whole curve into three equal parts,
superimposing these three parts and finding a third of the resultant
ordinates at each point of the abscissae. If this is a sine curve, its
maximum ordinate is E3. Again, to find E5, divide the whole curve into
five equal parts ; superimpose these parts and find a fifth of the algebraic
sum of the ordinates at each point of the abscissae. If this curve is a
sine curve its maximum ordinate is E5. The others, E^ E, . . . etc.,
can be similarly dealt with.

Due to a fault in the oscillogram, as mentioned in the paper by Mr.
Field, the distance o to t is not equal to the distance x to 2ir. Hence,
when looking for frequencies 3 and 5, he divided o to tt into 30 equal
parts, and also t to 2x into 30 equal parts. This gave him twenty read-
ings for the curve containing frequency 3, and twelve readings for the
curve containing frequency 5. None of the curves gave any indication
that a frequency 3 was present, but they all showed frequency $ quite
pronounced ; and considering the inaccuracy of the curves analysed,
the curves obtained in each case were fairly good sine curves. He now
tried for E„ by dividing each half of the curve into 33 equal parts,
giving him 6 points on the curve. All the three curves showed
frequency 11 very good. He had no time to try for any of the others.
The results he obtained were in arbitrary units : —

CuR\^ XVII.

Curve XX.

Cl'Rvk XXI.

/(E)„„ = 387

/(E)_ = 42-0

/(E)„^ = 34

E5 „ = 27

E5 „ = 1-2

E5 „ = 1-4

E„ „ = 09

E„ „ = 1-8

E„ „ = 4*2

He thought Mr. Field was quite correct in his main conclusions about
the nth and 13th, but he did not think he was correct in ignoring the
Vol. 82. 46

696 FIELD: THE PHENOMENON OF RESONANCE. [Glasgow,

ProfesstM-

Magnus

Maclean.

Professor
A. Jamieson.

other harmonics. Indeed, in Curve XVII., the fourth harmonic is
more important than the loth, though the reverse is the case in
Curve XXI.

In subtracting the harmonics so found from the original curve, it is
quite obvious that there are more harmonics in each of them than the
fourth and tenth. He believed from the appearance of them that there
are more harmonics than the fourth, tenth, and twelfth, but he had had
no time to work further at the curves.

Professor Andrew Jamieson said that any one who had carefully
studied such books as "The Alternate Current Transformer in Theory
and Practice," by Prof. Fleming, and the second or latest enlarged
edition of " Alternate Current Working," by Prof. A. Hay, the mathe-
matical parts of Mr. Field's paper were simple, clear, and explicit
Since he was dealing with actual concrete examples, the meaning of
several of the formulae were applied in a more telling manner, than will
be found in most treatises upon alternate-current testing and working.
Mr. Field had explained by blackboard sketches, in a clearer and more
detailed manner than that stated in the proof copy of his paper, the
principle, construction, and action of Duddell's oscillograph. He had
also dwelt upon its capabilities and shortcomings, and pointed out
how he overcame some of its defects. He might explain why he did
not photograph the various waves of E.M.F. and current straight from
the beam of light as reflected directly by the mirror which is fixed to the
two phosphor-bronze strips (upon, say, a moving cinematograph film)
instead of using the reflections from a second mirror, vibrated
synchronously with the first one, but at right angles to its axis ? Was
there no possibility of an error arising from the use of this special
motor and two such mirrors ?

Passing over the points touched upon by the previous speakers, and
referring at once to the condenser effect produced by electro-static
capacity of the underground main high-tension cables, between the power-
house and the sub-stations, they found the well-known formula (7) so
familiar to submarine cable electricians, viz. : — Current,. C = 2 ir « K V.
Then came equation (8), when a current was passed through a coil

having a coefficient of self-induction L, where current C = r •

^ 2 TT n L

And, when these were equated under the conditions stated, we got

Now, as to a mere matter of history, he had had the pleasure of con-
ducting a series of experiments, not only with Thomson and Jenkin*s
curb-sender, but also with Count Sicardi's curb-signalling key, leaks,
and other methods. The object of these experiments was to find out if
such devices minimised the retarding effects of electro-static capacity,
and thereby increased the speeds of signalling through the long sub-
marine cables of the Eastern Telegraph Co. There, of course, the
capacity effects were very much more pronounced than in the case of the
short main cables experimented upon by Mr. Field, but the frequencies
and the voltages were very much less. However, the increased speeds
so obtained by sending a reverse current after each signalling current.

1903.] DISCUSSION. 697

although apparent, did not justify the permanent introduction of any Professor
of these methods, since Muirhead's duplex system and Ben. Smith's A- J^*"**®*'"*
manual translation, which came to the front about the same time — viz.,
1876 to 1878 — showed better commercial results.* Then came Prof.
S. P. Thompson's proposal to introduce into the cable circuit, at stated
intervals, a certain anti-capacity effect by means of self-induction coils.
His idea consisted of arranging and fixing these coils to the cable
conductor, so that their self-induction should exactly or partially cancel
the electro-static capacity effects of the cable. But this bold proposal
did not meet with the approbation of practical cable engineers and
electricians, owing to the mechanical difficulties of lowering such water-
tight coils to the bottom of the ocean whilst paying-out the cable, and
of maintaining them in good electrical condition. He thought, however,
that this plan could be successfully applied to long subterranean tele-
graph, telephone, alternate-current lighting, or power transmission
cables. Mr. Field had shown how capacity and self-induction might be
so joined and adjusted, that the opposition to the current was merely
like that of a true ohmic resistance. But, then, his subterranean
cables were easily got at ; and if ever the " resonance effect " should
prove troublesome, or from prior investigation of the conditions
should appear to be in any way dangerous, the land electrician could
easily make suitable provision against the same.

It was a pity that Mr. Field was leaving Glasgow, because if he had
continued his experiments with the oscillograph and tried it directly at
the central station, the Section would in all probability have either had a
fresh paper or an appendix to his present long and weighty one,
stating whether or not the capacity of even two- or three-mile
lengths of the Glasgow tramway mains, between the central power-
house and any of the sub-stations, did appreciably tone down the
wave forms, as illustrated in the diagrams placed before us. He
(Professor Jamieson) thought the author had said, that he had not come
across a case wherein the resonance effect had proved dangerous to
such cables. He was under the impression that the first subterranean
cables put down at Londonderry, had been punctured or their insula-
tion resistance seriously diminished by some such action. With such
a splendid field for research, he hoped that the Glasgow Tramways'

• [I think that electricians who have opportunities of experimenting upon
long submarine cables or artificial lines should carefully study Mr. Field's
paper, as well as the experiments by F. Dolezatek and A. Ebelinz on the
" Pupin System" of long-distance telephony (see Electrician^ April and March,
1903). They should then try and devise the simplest and best combination of
oscillograph and cinematograph for delineating the curves of charging and
discharging or of signalling and of receiving currents, under a great variety of
conditions. They could vary the internal resistance and E.M.F. of their
sending batteries, the resistance and sensitiveness of their receiving instru-
ments, the capacities of their sending and receiving condensers, the periods
of curbing currents, the effects of introducing " Pupin Coils," etc. By trying
and systematically comparing the photographic curves derived from these
various changes upon cables of different lengths with different ratios of
capacity and resistance per naut, they would have a much more searching
and surer means of arriving at correct views upon the possibilities of
increasing speeds of signalling, than by any of the older methods hitherto
adopted.— A. Jamieson.J

698 FIELD: THE PHENOMENON OF RESONANCE. [Glasgow,

PiofMsor oscillograph would not be allowed to rest in its instrument case, but
A.jamic»oii. ^^^ .^ ^.^j^^ ^ ^^jj further skilfully applied to investigations such
as had now been suggested. It could not be placed in better hands
than one or other or both of the previous speakers, who would un-
doubtedly start fair and square at once at the very fountain-head,
where only the full pressures of 6,500 volts were to be found I They
must not, however, forget to earth the centre or neutral point of the
armature ; for it would be very sad to have to mourn their " loss."

At page 681, Mr. Field says, " We are now getting into the range of
the wireless telegraphist." But, surely, one of the principal objects of
the tramway or lighting electrical engineer is to keep as far as possible
away from such a range of voltage and frequency, when dealing with
dielectrics that would be sure to suffer from these effects. One of the
chief difficulties which Mr. Marconi had to surmount, was to ascertain
how best to arrange and proportion the values of his induction coils
and condensers, ithat for a given primary power he might obtain
the most effective electrical " splashes " across his " spark-gap."
Both Marconi and his colleagues had made many calculations and
experiments, and he understood that he required at Poldhu Station a
steam engine of not less than 150 B.H.P. to generate his sending
currents. This was, however, a mere nothing to the more powerful
Pinkston engines ; but happily their currents and circuits were not
similarly directed and arranged, or we should have wireless waves
sent right round the earth !
Ml. Hird. Mr. W. B. Bird said : The practical uses to which the oscillo-

graph might be put have been strikingly brought out in this paper,
and in this connection there was one point specially noticeable.
Mr. Field mentioned that he was unable to obtain good curves when
the conditions of the circuit were such as to produce resonance
and give great amplitude of the harmonics he was observing, because
the oscillograph motor under these conditions fell out of step. Some
years ago he had worked with a very rough oscillograph ; the curves
were obtained by passing the currents to be observed through long
wires stretched in a magnetic field, and carrying mirrors, the beam of
light from which was thrown, not as in the present instrument on a
vibrating, but on a rotating, mirror. The curve was thus drawn out in
a long trace, and by working in a dark room a photograph could easily
and simply be obtained on a sensitive plate or strip of bromide paper.
As many of the phenomena which it would be most interesting to
observe were obtained under conditions which were likely to throw the
oscillograph motor out of step, it would appear that some such
method of doing away with the synchronous motor would have some
advantages. Whilst quite agreeing with Mr. Field that a 12th or any
even harmonic is inadmissible in curves obtained from the generators^
he described, because it would make the positive and negative halves of
the curves dissimilar, he saw no reason why such a machine should not
produce current curves in which the right and left halves of each half-
period were unsymmetrical, and he therefore did not sec that the fact
that an even harmonic would produce such want of symmetry could be
quoted as an additional reason for the absence of such harmonics.

1903.J DISCUSSION. 699

Mr. Field, after giving his very ingenious explanation of how the nth Mf-**^"*-
and 13th harmonics in each of the three phases combine to give 12
ripples in the D.C. curve, said that no other pair would combine in the
same way ; it seemed, however, that the 5th and 7th harmonics, if
present in each of the three phases, would combine to form 6 ripples,
and the 17th and 19th to form 18 ripples, in exactly the same way,
and using the same reasoning as that by which it is shown that the
nth and 13th combine to give 12 ripples. It would be extremely
interesting to examine the D.C. curves, and to attempt to increase the
amplitude of these harmonics, say, by resonance, so as to detect either
6 or 18 ripples in the curve ; and if such were discovered, this would
be a striking confirmation of Mr. Field's theory of the genesis of these
ripples.

Mr. S. Blackley said : After such a lengthy paper, it was very Mr.
difficult to add anything further to try to satiate the desire for informa- ^ '
tion on this interesting subject, as Mr. Field has suggested that he
should do. Resonance was a most fascinating property of the electric
circuit, and the importance of its effects on alternating-current systems
was frequently under-estimated, if at all considered. It was usually
stated that, in practice, the danger accruing from resonance was a
myth, or that, no bad effects having resulted so far, the system under
consideration was immune from danger of this kind. When they
considered that the insulation of our electrical plant and cables must
be deteriorating to a certain extent as time goes on, and remembered
that in a high-tension system, consisting, say, of transformers, induction
motors, and perhaps fifty or sixty miles of good capacity-giving cable,
the resonating combinations which might occur are numerous, they
should keep in mind the possibility of trouble from resonance effects.
He should reconmiend any one who was inclined to be sceptical on this
question to endeavour to obtain a glimpse of the effects (as shown by
an oscillograph) which a resonating harmonic of even a moderate
frequency had on the E.M.F. wave of an alternator on ho load, or to
watch the arc formed on opening a high-tension air-break switch in
the circuit in which resonance existed. On switching on a few high-
tension feeders he had seen the 13th harmonic in Curve XX. resonate
to such an extent that all semblance to the original wave form had
disappeared, and slightly undulated sinusoidal wave of great amplitude
and of a periodicity of 325 cycles per second had taken its place. The
question naturally occurred — What would happen if they had a small
polyphase synchronous motor running light on this circuit when these
cables were switched on ? Would the motor, with its field not too
strongly excited, prefer to stand still or to speed up to synchronism at
the higher frequency ? In either case, if they had no previous knowledge
of what was going on in the circuit, he expected that the result would be
attributed to the speed variation of the engine. Previous to Mr. Field's
experiments he had frequently noticed, but could not account for, the
sparking which was exhibited all over the high-tension feeder circuit-
breakers in the sub-stations as the main engine was starting up in the
morning or slowing down at night. This sparking seemed to be statical
in nature, and occurred between the woodwork and iron fittings of the

700 FIELD : THE PHENOMENON OF RESONANCE. [Glasgow,

Mr.
lilacklcv.

Dr. J. B.
Henderson.

circuit-breakers. On investigation it was found that the phenomenon
always appeared and disappeared at a certain voltage, lower than the
normal, as indicated by the high-tension voltmeter in the sub-station,
the needle of the instrument remaining stationary for a few seconds
while the sparking lasted.'^*- Immediately after the sparking had ceased
the voltage began to rise gradually, and nothing further was noticed •
They then examined the E.M.F. wave by means of the oscillograph as
the voltage fell at night, and found that sparking commenced when
the main engine reached a speed such that the frequency correspond-
ing was of a value suitable to produce resonance of one of the
harmonics in the wave. The wave form was very similar to that
shown in Curve XV^. From a consideration of the formula for
resonance, viz., i = 4 tt* «" K L, the above result would be expected.
Since adopting Mr. Field's suggestion as to starting up or shutting
down on the high-tension side the sparking had disappeared,
except at the normal voltage of 6,500, and only then when a certain
length of cable was in circuit. On page 667 Mr. Field referred to the
method of arriving at the capacity of the cables by measuring the
charging current flowing into them. Perhaps it would be vnsc to
explain that they only expected to arrive at an approximate value of the
capacity by the method indicated. The inconsistency in the results
was largely due to the fact that the E.M.F. wave of the alternator was
not sufficiently near the sinusoid in form to admit of the use of the
formula C = 2 irn V K/io^ The results served, however, to show how
utterly unreliable this method of determination of capacity was even for
approximations. It was well-known that the capacity current would be
a minimum when the alternator used gave a pure sine wave. In a later
test, which he had not had an opportunity to confirm, he measured the
current flowing into the cables when the capacity was such as to give
t^e conditions indicated by Curve XX. and again under conditions of
more pronounced resonance than in Curve XV. Strangely enough, the
results were only consistent if, in the former case, they calculated the
capacity using 25 as the value of the frequency, while in the latter
the frequency is Jaken as 13 by 25. The capacity values determined
only vary by 3 per cent., the higher value going with the higher
frequency.

Dr. J. B. Henderson said that Mr. Field assumed that the ripples on
the alternator E.M.F. wave consisted of sine curves superposed on the
fundamental. This might not represent the facts in every case, but it
was an assumption as justifiable as that the E.M.F. curves of our old
alternators were sine curves, and it might lead to some important general
conclusions. Working on this assumption, he had calculated the
harmonics, up to the 29th, which were present in the ripples shown in
Figs. 7 and 8. Mr. Field had already calculated some of those present
in Fig. 7, but it was Fig. 8 which represented the E.M.F. curve of each
phase winding of the alternator. The ripples, however, which Mr.
Field traced by means of the oscillograph were the ripples on the line
E.M.F. curve, and as the alternator windings were connected in star,

• The voltmeter used was of a type which would not read correctly at all
frequencies.

1903.] DISCUSSION. 701

they were the ripples which resulted from combining two of the curves, Dr. j. b.
like Fig. 8, at 6o° phase difference. If we represented the amplitudes "<^°*^<^»^n-
of the ripples in Fig. 8 by i, 2, 2, 2, 2, i, the amplitudes of the
ripples in the resultant wave were i, 3, 4, 4, 3, i. It was interesting to
notice that all harmonics which were multiples of 3 disappeared by a
combination in star and were magnified by a combination in mesh, so
that they would cause currents to circulate in the delta. The accom-
panying table gave the values of the harmonics up to the 29th in the
three cases which he had mentioned. It would be noted from the last
column that on the line wires the harmonics 11 and 13 were more than
thirty times as important as any of the others, except, of course, the
first, which S3mchronised with the fundamental, and was therefore of
no account in our comparison. Professor Maclean was, he understood,
analysing some of the actual oscillograms taken by Mr. Field. If
his analysis did not agree with the last column it simply proved that
the sine curve assumption was wrong for this particular alternator. In
analysing these ripples he presumed that Professor Maclean had, first
of all, corrected the curves for the errors of the oscillograph which
Mr. Field mentioned in the paper, as the inequality in the horizontal
scale of the oscillogram would introduce much more serious errors in
the analysis for the higher harmonics than for the lower.

When we considered the combination of three similar line E.M.F.'s
in mesh connection as in the rotary converter armature, the harmonics
also combined at phase differences which depended on the particular
harmonic considered. The phase difference in the n^ harmonic was
n X 120". We found then that the harmonics i, 7, 13, i9i 25, etc., com-
bined at -h 120° phase, while the harmonics 5, 11, 17, 23, etc., combined
at — 120° phase. If therefore the fundamentals gave a rotating field in
one direction, the harmonics 7, 13, 19, 25, etc., would give rotating fields
in the same direction, and the fields due to the harmonics 5, 11, 17, 23
would rotate in the opposite direction. The speed of field rotation was,
of course, proportional to the frequency. By reasoning similar to that
used by Mr. Field for the nth and 13th harmonics applied to the rotary
converter, we saw that there would be ripples on the direct-current
E.M.F. of the rotary having 6, 12, 18, 24, etc., waves per period of the
alternating current. Since these were all even harmonics, the direct-
current curve should always be a smooth curve, no matter how angular
the E.M.F. cur\'e on the alternating side might be with its odd har-
monics. The D.C. Curves III., X., and XI. were a strong confirmation
of the much greater intensity of the nth and 13th harmonics than of
any of the other harmonics in the A.C. E.M.F., and these curves there-
fore tended to confirm the figures given in column 14 of the above table.
He had to thank Mr. Field for giving him the opportunity of discussing
this excellent paper, in which he felt a great interest, as he had con-
versed with him from time to time about the work, and had been
privileged to watch the actual changes taking place in the E.M.F.
waves as the cable system was altered.

702

FIELD : THE PHENOMENON OF RESONANCE. [Glasgow,

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1903] DISCUSSION. 703

Professor A. Gray said that he had read Mr. Field's paper with P«>f.Gray.
much interest, and regarded it as an example of the benefit to be
derived from a free use of Mr. Duddell's beautiful instrument. When
once the curves had been thus drawn, the well-known methods of har-
monic analysis could be at once applied to separate out the harmonics
which existed in the wave forms, and thus to exhibit the fundamental
components of the action of the machines. This was a further step of
some importance, and perhaps some of the mechanical analysers which
had been devised for periodic curves might be made use of in this con-
nection. It was only by such registration of the behaviour of machines
and subsequent analysis that w^e could obtain light upon the various
matters which were still obscure in the action of generators of different
kinds. He had felt specially interested in the discussion on resonance,
and in that part of the paper dealing with the alternating charge and
discharge of cables. The curves, though small in scale and therefore
difficult to examine closely, were almost surprisingly identical with the
cur\'es that one could draw for the oscillatory subsidence of the charge
of a condenser from the theoretical equation, obtained by supposing the
plates connected by a coil of definite unvarying self-inductance. The
crests of the successive ripples lay on the exponential curve {e,g,, Figs.
24, 26, etc., if it was that these had been drawn for actual cases by
discharge through the inductive coils of a machine) which one would
have expected in such a case. Now, the self-inductance of the circuit
cquld not be constant in this case, but must be some function of the
current, and therefore of the time ; and the exact solution of the
differential equation could not be given unless this function was known,
and almost certainly only by approximation even then. He would Hke
to see a large scale of curves for this case. In the meantime, it was
interesting to have the results given in the paper. The fact that the
potential on a cable at charge or at discharge might be very much
greater than the working j)otential was, of course, a result that might
have been anticipated without experiment, but Mr. Field's exhibition
of it in this way must be of great value to practical men in calling
attention to the matter, and in causing those in charge of plant of this
description to realise the danger that probably had not occurred to
anybody.

There were a good many corrections required in the proof, which
would no doubt be made by the author, and he did not desire to make
these in any way a matter of criticism. But some of the more mathe-
matical slips should be carefully scrutinised. There were some points
in connection with the curves which he had not yet had time to
consider, which he should like to go into at some future time — for
example, as to curves XXXVI., which were very interesting.!

The only other remark he would make at present was as to the
definition of self-inductance. There were two definitions current ; one
was the equation

E=RC + L^ (0

in which it denoted the coefficient of the time rate of variation of the
current dCldi in the expression for the electromotive force in the

704 FIELD; THE PHENOMENON OF RESONANCE. [Glasgow,

Prof. Gray, circuit. In a circuit containing iron, of course, L was not a constant, but
was the rate of variation d N/d C of the total number N of lines of force
through the circuit with variation of the current C. This definition had,
no doubt, its advantages for dynamo work, otherwise practical men
would not employ it, and he was not to be taken as objecting to it. But
there was the other sense in which the term self -inductance had been
employed by most of the pioneers in electro-magnetic theory ; the
defining equation was here

N = LC (2)

where N had the same meaning as before, L was not here a constant
either, and its relation to the L of the former equation was easily exhi-
bited. We had clearly from the equation just written

rf N _ rfN dQ
dt — '* dC di

\ ^ dd dt

by (2), so that if we denoted the L defined by equation (i), that is
d ^jd C by L', and use L for the quantity defined by equation (2), we
had—

L'= L + C -'^^.
d C

The difference was that V united in one symbol the two parts of the
coefficient of d Cjd t in the equation of electromotive force (i) ; and the
two values coincided in the case of constant self-inductance. As he had
indicated, there was this double use of the term self-inductance, which
was, he thought, a pity. One definition was as directly applicable to
alternating circuits as the other ; the important thing to remember in
either case was that when there was iron present the self-inductance
was variable. The matter was entirely one of definition, and in that
the convenience of all concerned should, of course, be consulted.

Perhaps it was unnecessary, but there was no warning given, so far
as he could see, that the whole mathematical disquisition commencing
on page 677 to near the end proceeded on the assumption that L was
constant, which, of course, it was far from being in the circuits of the
machines usually employed in the work referred to.

The paper represented a vast amount of good work, though in its
present uncorrected form its complete perusal was a matter of consider-
able difficulty. He hoped that it would be printed, so that its results
might be fully understood and appreciated.

1903.] TRANSFERS, DONATIONS TO LIBRARY, ETC. 705

The Three Hundred and Ninetieth Ordinary General
Meeting of the Institution was held at the Institution
of Civil Engineers, Great George Street, Westminster,
on Thursday evening, March 12th, 1903 — Mr. James
Swinburne, President, in the chair.

The minutes of the Ordinary General Meeting of February 26th,
1903* were, by permission of the Meeting, taken as read and signed by
the President.

The names of new candidates for election into the Institution were
also taken as read, and it was ordered that their names should be
suspended in the Library.

The following list of transfers was published as having been
approved by the Council : —

From the class of Associate Members to that of Members —

Ralph Henry Govern ton.

From the class of Associates to that of Associate Members —

Alfred S. L. Barnes | Andrew Stewart.

George Richard Drummond. t E. Taylor.
Richard Christopher Simpson. | H. Osborn Wraith.
Warwick Makinson.

From the class of Students to that of Associates-
Harold Thomas Brown. | Frederick Edward Kennard.
Cuthbert John Greene.

Messrs. Quin and Speight were appointed scrutineers of the ballot
for the election of new members.

Donations to the Library were announced as having been received
since the last meeting from the Italian Ambassador ; to the Building
Fund from Messrs. R. C. Barker, J. R. Bedford, W. J. Bishop, R. H.
Burnham, A. D. Constable, R. A. Dawbarn, F. W. E. Edgcumbe,
W. Fennell, A. G. Hansard, E. R. Harvey, C. E. Hodgkin, G. F. R.
Jacomb-Hood, Lord Kelvin, H. Kilgour, H. Lea, A. E. Levins,
F. H. Nicholson, M. Robinson, H. Seward, F. W. Topping, C. E. Wigg,
and A. P. Whitehead ; and to the Benevolent Fund from Messrs. W. J.
Bishop, R. V. Boyle, M. S. Chambers, K. W. E. Edgcumbe, J. W.
Fletcher, Prof. R. T. Glazebrook, E. P. Harvey, A. E. Levin,
M. Robinson, A. P. Trotter, H. J. Wagg, and R. W. Weekes, to whom
the thanks of the meeting were duly accorded.

706 WIRING RULES— TELEGRAPH CONFERENCE. [March 12th,

The President : It will be within the knowledge of many of the
members that the Council has been engaged for some time past in the
preparation of Wiring Rules. A committee has sat and worked very
hard in connection with the subject, and we have now drafted a set (^
Wiring Rules, which have been passed by the Council, having first
been dealt with word by word by a very large and representative
Committee. The Wiring Rules have been submitted to the Incor-
porated Municipal Electrical Association, which, after making some
slight alterations and improvements, has adopted them. That body
had a representative on the Committee. Several of the largest Fire
Insurance Companies have also adopted the Rules. The Wiring Rules
at present issued by different bodies are not only divergent, but in
some cases incompatible with the new set of Rules as drawn up by this
Institution. We hope that our Rules will gradually supersede others,-
and introduce uniformity in standardisation. It is proposed to send
them to supply engineers, consulting engineers and the Power
Companies and contractors, and it is hoped that members will use
every possible effort to get the Rules adopted, and will use them
themselves whenever they possibly can, and so gradually get them
introduced universally. A Standing Committee has been appointed, so'
that if any alterations arise from time to time they can be dealt with as
they arise. It will not be necessary to wait until there is any very
large improvement needed. Any small alterations can be made
practically at once if it is found necessary.

There is another matter which has been before the Council for some
time to which I desire to draw attention, namely, that a Telegraph
Conference is to be held in England in May or June of this year.
Most of us in our days come to listen to papers in this Institution
which are not Telegraph papers, but we must remember that
Telegraphy was the original work of this Institution. We were
originally a telegraph society, and although we do not now get so
many papers and novelties on the subject of telegraph work, telegraphy
is by no means correspondingly unimportant. In fact, it is the other
way about ; telegraphy has got to such a high pitch of perfection that
there is very little to bring forward before the Society. Telegraphy is
of enormous importance to this Institution. I may remind you that
this Congress is an International affair, and will be a very large and
important gathering ; the Council therefore feels that we ought to do
everything we can to entertain the Congress, and to take our proper
part in the proceedings. But a difficulty at once occurs, because it
will be held at the end of one session and the beginning of the next.
The Council feels, and has felt all along, that the right thing to do is to
have one President to take charge of the Institution over that time, and
to have a President selected for that purpose. There is one man in
particular who is exactly the right man to be President under those
circumstances, and I have little doubt the Council will select him. In
order that the Council may have the opportunity of selecting a
President, and of his being elected so as to preside during the
Congress, and to give him ample time to make the needful prepara-
tions, I propose to send in my own resignation between this and the

1903.] CONSTABLE & FAWSSETT : DISTRIBUTION LOSSES. 707

next meeting. Then, by the Regulations, the Council will be able to
nominate their own new President, who will take charge on that election
until the General Meeting. After the General Meeting, of course, the
President has to be nominated and elected in the usual way by the
Institution ; but when you know whom the Council proposes as
President I know you will be unanimous in electing him for the
following year also.

I will now call on Mr. Fawssett to read the paper which he has
written together with Mr. Constable. It is most unfortunate that Mr.
Constable is very seriously ill. He was not able to be here on the last
occasion, and he is not able to be here to-night, but we hope very
much he will be able to be present at the next meeting, and give him
our best sympathies.

DISTRIBUTION LOSSES IN ELECTRIC SUPPLY

SYSTEMS.

By A. D. Constable, Associate-Member, and
E. Fawssett, Associate.

" Dare quant accipereJ* This is a motto not universally followed by
electrical engineers in the course of their business, yet in the case of a
particular supply- station of quite moderate capacity, over 800 tons of
coal are annually given gratis to warm up the town, and the authorities,
besides not receiving one penny towards the cost of it, do not even
receive the thanks of the residents for the grateful warmth provided.

Few central "station engineers expect to get paid for more than
75 per cent, of the energy they generate. Of the remaining 25 per
cent, about four-fifths is absolutely wasted ; and worse than that, it
increases the waste which would otherwise take place. The other
fifth is used in the station itself for lighting and other purposes, and
cannot be said to be actually wasted, although it is unproductive as
regards revenue.

It is worth while considering how this wasted 20 per cent, is made
up, and whether it is possible to reduce it in any way, since it costs as
much to generate each unit wasted as each unit sold.

The figures given in this paper refer to the Croydon Electricity
Works.

The total losses incurred between the generator terminals and the
consumers' terminals, leaving out of consideration the units used in
the station for field excitation, lighting and driving auxiliaries, may be
subdivided under the following five headings : —
(i) Losses in Switchboards and Connections.

(2) Losses in High Pressure Feeders.

(3) Losses in Transformers.

(4) Losses in Low Pressure Cables.

(5) Losses in Meters.

These are discussed under the various headings, Nos. 2 and 4 being
taken together.

708 CONSTABLE AND FAWSSETT : DISTRIBUTION [Mar. 12th,

Switchboard Losses.

Notwithstanding the fact that we are not dealing with a material
substance like gas, which has to be conveyed through pipes with
innumerable possibilities of leakage, there is an actual loss in trans-
mitting electrical energy to the consumers of over 20 per cent, of the
total energy sent out of the station.

The actual loss by leakage is extremely small ; by far the larger
part is, of course, due to our having no perfect conductors at our
disposal, and this loss due to conductor resistance is infinitely more
important than the corresponding loss of pressure due to pipe friction.

TABLE No. I.
Losses Up To axd Including Main Switchboard.

S>'stem of Supply.

Maximum Output.

Approximate Mean Loss

in per cent, of Annual

Output.

2,000 volts alt.

I '

cur. one pole
earthed.

500 volts direct

[ 1,250 K.W.
)

0-43

cur. Tramways
(A)

500 volts direct

V 500 K.W.

0-42

3 ]

cur. Tramways
(B)

t 400 K.W.

0-30

Average loss in Substation Switchgear (System i) and connections :
o'lo per cent, of output.

It becomes appreciable even at the feeder terminals on the main
switchboard. Table I. gives these initial losses in the case of three
different sets of plant. The values were obtained by measurement,
and may be taken as a very fair average of the usual existing con-
ditions. Careful arrangement of the relative positions of the switch-
board and generators and simple design of the switchboard will, to
some extent, eliminate these losses.

The minimum number of instruments should be installed, and these
should be connected with as few joints as possible ; ammeters should
preferably be of the shunted type. Some switchboard erectors have a
natural incapacity for screwing connections up tight, and some instru-
ment makers are afraid of giving their customers too much metal ; the
authors have come across several cases of joints which have welded
themselves together, of bus-bars running at or over 200° F., and even
of switch-gear working at a temperature of 150° F. at normal full load.

One square foot of dull copper surface running at 10" F. above the
temperature of the air will continuously dissipate the heat produced by

1903.] LOSSES IN ELECTRIC SUPPLY SYSTEMS. 709

the absorption of about i6 watts, or, if the excess temperature is 50° F.
the watts will be about 60.

Main fuses should be avoided where possible, not only because they
■ are objectionable in themselves, but to be of use they must run warm
and consequently waste energy.

It may be said that these are refinements beneath the notice of the
practical engineer, but in the station under consideration, which is of
fairly modern design with an output of only 1,250 k.w. at the maximum,
the total loss per annum in the switch-gear and connections alone
(including those in the substation) amount to 10,000 units, which, it
will be readily granted, shows considerable room for improvement.

In those cases where the generator pressure is raised before trans-
mission, in addition to the switchboard losses there are those in the
step-up transformers to be taken into consideration ; these are dealt
with in the section on transformer losses later on.

Cable Losses.

Of all the losses in the system, the cable losses are the most
important and those that can be least easily reduced. The larger part
of this paper will, therefore, be devoted to their consideration.

The total losses in the cables may be split up into three com-
ponents : —

(i) CR losses in the dielectric.

(2) CR losses in the conductor.

(3) Losses due to what may be called dielectric hysteresis.

The first may be shortly dismissed ; it is, as stated above, generally
very small, at any rate in the main feeders of a well laid out system.

The total insulation resistance between poles of this system of
2,000-volt feeders, comprising about 25 miles of concentric cable in
nine separate feeders (ranging from '150'' to '0250") was o'lo-^,
including switchboards at both ends. This, at a pressure of 2,000 volts,
corresponds to a total leakage current of 0*02 ampere, or a loss of only
40 watts, or 350 units per annum, i.e., 14 units per mile of high-tension
cable.

The insulation of the low-tension network is, of course, very much
less, and can, with difficulty, be measured ; if we include all switch-
gear, network boxes, and services, it may be about 1,000 w for 50
miles of cable, and at 200 volts the lost watts will be again 40, or 7
units per mile of cable per annum. The 50 miles of low-tension cable
roughly correspond to the 25 miles of high-tension cable, so that the
total leakage loss is only 700 units per annum.

The above figures give a rough idea of what may be expected in
this direction, and it is useless to go into greater detail, owing to the
enormous variations of insulation met with in practice. The insulation
of a low-tension network may be of the order of ohms without being
detected, for a long time. A case in a neighbouring system once came
under the authors' notice in which there was a leak sufficient to raise
a mass of concrete round a bunch of cables to a red heat before it was
noticed ; this is, happily, a very exceptional case.

710 CONSTABLE AND FAWSSETT : DISTRIBUTION [Mar. 12lh,

The second cause of loss, viz., that due to C*R in the cables, is of
the greatest importance, and it also lends itself, in the case of feeders
at least, to fairly accurate calculation. In the case of the low- tension
network, however, the loss can only be approximately ascertained.

Table II. gives the C'R losses for the whole of the Croydon system
of mains. They have been worked out for each quarter of the year,
the basis of the calculation being the load curves shown in Diagram
No. I. The upper full curve is the load curve for a December
week-day. The lower curve is the load for a day in July, and the
middle curve is the mean for September and March. The curve for
March is rather higher than that for Septembei^ owing no doubt to the
latter being the holiday season. In working out the losses, these
curves have been assumed to be the mean curves for the corresponding
quarter, and the current in each separate feeder and distributor has
been assumed to follow the same law as the total current.

TABLE No. II.

CR Losses in Cables.

Maximum Load Supplied : 1,250 K.W.

Description of Cables.

CaR T/>ss in Units per

Annum.

2,000 volt Feeders and Sub-feeders. About
25 miles, 0*15 sq. inch section to 0025
sq. inch

400 and 200 volt Distributors. About 50
miles, 040 sq. inch section to o'lo sq. inch

H.T. Arc Cables, io*6 miles, 0*023 sq. inch
Section (series)

L.T. Arc Cables. About 20 miles, 006 sq. inch
and 0*025 sq. inch section

Total

47,200

66,200

IMOO

25,800
150,600

This is, of course, not strictly accurate, but is near enough for the
purpose of this calculation. An exception has been made in the case
of the public lighting load, as this, of course, follows a different law.
The lower dotted lines in the diagram are the load curves for public
lighting, and are calculated from Diagram No. II. as a basis, there
being in this case a total of 400 arc-lamps, 180 of which are switched
off at about midnight. The greater part of these lamps are fed in
parallel at 200 volts alternating, from low-tension mains used for no
other purpose.

1908.]

LOSSES IN ELECTRIC SUPPLY SYSTEMS.

717

o
o

o
in

^•^'

.-.-•

..-•-'

1
1

_^_

,-r'*''

.-'

?or*"

(

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tXX>IM01l)4

xndxno

Vol. 82.

712 CONSTABLE AND FAWSSETT : DISTRIBUTION [Mar. 1^

These mains, however, take their supply from the same low-tension
bus-bars in the substations as the private supply. There are in addition
four high-tension series circuits supplying together 134 lamps.

The upper dotted curves are the private lighting load curves for the
respective quarters, and are used to calculate the C'R losses in the low-
tension network, in conjunction with the observed average drop in
potential between the substations and consumers' terminals, which
latter averages four or five volts.

We now pass on to the third heading — " Losses due to dielectric
hysteresis," to use the term for want of a better one. After the very
thorough way in which this question was discussed recently before this
Institution, perhaps an apology is needed for again bringing up the
subject. As the question was not finally settled, it was the intention of
the authors to experiment thoroughly on the large system of high-

HOURS or PUBLIC UCHTINC

JAN

iMN

PFS

FTB

MAR

NAX

APR

¥K

JUNE

lur

JUY

;

•nr

AUG

tin

«n

OCT

NOV

OPR

(

i i

i '

(

1 ]

1 »

0 1

t NO

NT.

^'i

\ i

1 i

\ 4

(

1 1

i HOOi

Diagram No. II.

tension cables at Croydon, and find out once for all what the true
losses incurred in actual working were ; an additional incentive was the
desire to again demonstrate that, contrary to the usual belief, it was
possible in certain cases to obtain a power-factor as high as o'lo in a
cable, as was stated to be the case in Mr. Mordey's paper and in
Mr. Minshall's contribution to the discussion thereon. The latter is
conclusively proved by the figures in Table IV.

The more ambitious scheme was doomed to partial disappointment
at any rate ; it has been found a task of very great difl&culty to obtain
these losses with any reasonable accuracy with the instruments available
in a fairly well equipped test-room. Numerous experiments have
been made, but owing to the interruptions due to the necessary routine
of work of a central station in an exceptionally busy year, these results
are somewhat meagre and inconclusive. This section of the paper is,
therefore, rather of the nature of a series of suggestions, and it is hoped
that the discussion will produce further data.

1908.]

LOSSES IN ELECTRIC SUPPLY SYSTEMS.

713

The experiments are here discussed seriatim, as some of the
methods adopted and the difficulties experienced, as well as the few
results obtained, may be of interest.

The methods available for this investigation are : —
(i) Direct measurement of watts used in the cable by a wattmeter
either with or without a choker to improve the power-factor
of the circuit.

(2) Calculation of watts from plotted curves of volts and current

or from oscillograph records.

(3) Direct measurement of increased power necessary to drive an

alternator when a cable is switched on.

(4) Calorimetric method, i.e., measurement of rise of teipperature

due to lost watts.

(5) Calculation of watts lost from known data and law of current

variation determined experimentally.

ZJDOO VOLT BUS -BAR

Earth bar.
Diagram No. III.

The first three methods have been used in this investigation with
the results discussed below. Method (4) is one difficult of application
and impossible in the case of cables in the ground, and is in any case
open to many sources of error.

Method (5) has not been attempted, as sufficient data as to the law
of current variation have not been obtained.

With regard to method (i), the first thing necessary was to discover
what reliance could be placed on the readings of the ordinary com-
mercial wattmeters at our disposal, when used on various power-
factors.

Three wattmeters were used, viz. (i) a Swinburne with no unneces-
sary metal parts. This wattmeter had three different sets of current
coils to give different sensibilities. (2) and (3) Thomson inclined coil
wattmeters of different ranges with frames partly of metal. All three
had large non-inductive resistances in series with the pressure coil, and
were wound for 250 volts.

714 CONSTABLE AND FAWSSETT : DISTRIBUTION [Mar. 12th,

TABLE No. III.
Wattmeter Constants.

Date.

17-7-01

4-8-01
6-8-01

17-8-01
6-8-01

17-8-01

4-8-01

17-8-01
8-901

10-9-01

4-8-01

7-8.01
6-9-01

4-8-01
6-9-OI

6-901
17-8-01

Nature of Load.

Non-inductive Lamp
bank

do.

do.
Inductive, Current
leading

do.

do.
Do.. Cur. lagging ..

do.

do.
Do., Cur. leading ..

do.

Do., Cur. lagging ..

Do., Cur. leading . .

Non-inductive lamp

bank

THOMSON WATTMETER

Power
Factor.

Con-
sUnt.

Scale
Rdgs.

Voltage
Curve
similar
to

SWINBURNE WATTMETER.

No. 10

Sheet

12. St B.

1N0. 10
Sheet
A.

No. 10
• Sheet
A.
No. la
Sheet a
No. 10
Sheet A.

No. 10

Sheet

la.St. B.

10, St A.

roo

992

100

1005

i-oo

983

x-00
100

9-90

9-88

1*00

9*93

I -00

i-oo

lo-ox

I -00

o-iag

9*03

0-374

9-98

0*141

10-20

0143

IO-I7

0033

0304

0034

10-26

2*5

O-03S

10-90

a-5

0-129

1-262

0-129

1195

0-143

1-256

0-142

1193

0-034
0-I38

0952

1-189

X-000

1-278

70-90

AMP. RANGE.

Non-Inductive Lamp
Bank

do.

do.
Induc-Cur. leading

do.
Do., Cur. lagging

do.

»p

I'OO

1-027

140 {

I-oo

100

60-140 J

100

1-063

140

0-I4I

1-016

0-I4I

1-040

0-032

1-271

0-304

1*026

150

0035

1-015

. No. 12
Sheet B.
No. 10
Sheet

No. 12

Sheet B.

la St. A.

THOMSON WATTMETER. 10 AMP. RANGE.

Non-inductive Lamp

Bank .. 1*00

do. . . 1*00

Inductive, Current

leading . . 0*142

do. . . 0143

Do., Cur. lagging . . 0*035

978

9*96

No. 10.
Sheet

6-60

• A.

7-81

8-83

Remarks.

Original Fme Wire ,
Current CoU.
about No. 16
S.W.G.

Current Coil re-
wotmd with fine
vrire, about No.
26. S.W.G.

Cur. C<ril rewound
as above,andal»o
new vc^colL

As used in all ex-
periments after

4-8-01.

Not used owing
to variable con-
stant

The voltage was reduced in the ratio of about 10 : i by means of a
bank of lamps, the actual ratio being measured for each set of readings ;
the voltage on the wattmeter was measured on a standard electrostatic
instrument, and the full voltage was reduced by a transformer of known
ratio and measured on the same voltmeter.

Diagram No. III. shows the connections for calibrating the watt-
meters initially ; it is almost self-explanatory, and power-factors of
about 0-03 and 0-35 with current lagging, 0*14 with current leading,
and unity were used in the calibration. The leading current was

1908.]

LOSSES IN ELECTRIC SUPPLY SYSTEMS.

715

obtained by passing a current through the series coil of the wattmeter
in phase with the applied volts and connecting the pressure coil to a
non-inductive resistance in series with a choker. The wattmeter is
§hown connected in this way in the diagram.

The power-factor of the ironless choker circuit of course can be
calculated with very fair accuracy. The choker, as used throughout,
consisted of 112 lbs. of No. 16 copper wire wound on a wooden drum.
A thermometer was embedded in the winding and the temperature was
taken for each reading.

The resistance, in series with the choker, consisted of lamps. It
has been assumed throughout that the lamp banks used were non-
inductive, no difference in phase between current and applied volts
being observable on the oscillograph used in these experiments.

Table III. gives the constants obtained for the wattmeters under
the various conditions.

2.000 VOLT BUS- BAR

]n([] NN' tWi#i#iJ

Diagram No. IV.

It will be noticed that the Swinburne Wattmeter and the small
range Thomson Wattmeter give fairly consistent results, although there
are considerable variations with the different power-factors, chiefly
due, in all probability, to the various wave-forms of the applied voltage.
There are also variations in the constant obtained under the same
conditions at different times, but as the constant used in working out
the cable watts was that obtained under the most nearly corresponding
conditions, and at the same time in most cases, the errors should not be
large. Very low power-factors with leading current were not obtain-
able for calibration owing to the lack of a larger choker.

In the case of the larger range Thomson instrument the constants
vary from 6*6 to nearly lo'o, notwithstanding the maker's statement
that the instrument is correct for all power-factors and all wave-forms ;
this apparently applies between certain limits only. The readings of
this instrument were, therefore, rejected. In the later experiments by

716 CONSTABLE AND FAWSSETT : DISTRIBUTION [Mar. 12th,

a slight modification of the connections it was possible to calibrate the
wattmeter, in use, on a load with leading current, for every reading,
and this was done in each case.

The actual connections used in the cable experiments are shown in
Diagram No. IV., two wattmeters being generally used in series as a
check.

Readings were taken, both with and without the choker C in
parallel with the cable.

L in the diagram is a bank of lamps, used in the earlier experi-
ments in calibrating the wattmeters with PF = i. The ammeters
were all compared with a low-reading Siemens Dynamometer, but
the final standard was an Elliott's Voltmeter, used in conjunction
with a standard ohm.

The arrangement on the right of the diagram at the bottom is for
the purpose of calibrating the oscillograph. A voltage of 130 D.C.
could be applied to the oscillograph without altering the connections
and the value of the deflection in volts thus obtained.

In the same way a known direct current could be passed through
the non-inductive current shunt R, and the value of the oscillograph
deflection in amperes ascertained.

The principal results obtained are given in Table IV., and the
agreement of the watts absorbed in the cable as measured by the
wattmeters and by working out the oscillograph curve, is in some
cases good. These curves were worked out by taking the mean value
of the instantaneous watts for 22, and in some cases 44, equi-distant
points of time in the diagram of one complete period.

In several instances it will be noticed that the R.M.S. value of the
voltage obtained from the oscillograph diagrams is higher than that
measured on the voltmeter. This is probably due to the fact that the
calibration was made with 130 volts instead of 200 volts, and the re-
sistance of the lamps in series with the voltage strip was higher than it
was in the actual experiment, thus making the oscillograph appear less
sensitive than it really was.

In the case of Experiment No. 15 and onwards this possible error
did not occur, as there were no lamps in series with the voltage strip,
and the agreement is better, though in this case the voltage as measured
is slightly higher than that obtained by working out the curves.

The watts taken by the choker alone have been also worked out
from the oscillograph curves (Curves D), and the agreement with the
calculated watts is in this case good.

Some experiments had to be made without the oscillograph, owing
to its being out of order, so that in these cases the watts are only those
obtained on the wattmeter. Some were made without a wattmeter
and some without independently calibrating the oscillograph (see last
column in Table IV.). In the four cases in which watts have been
obtained, both from the oscillograph records and with a wattmeter,
the two values are of the same order, but they do not agree as well as
could be wished.

This is, no doubt, explained partly by the shape of the waves. In
curves of shapes E, F, and G, for example, owing to the almost vertical-

Exp.

Date of

Cable

No.

Experiment.

No.

21-7-OI

8-9-OI

8-cH)l j

I4-7-OI i

2I-7-OI i

4-8-OI

2I-7-OI

4-8-OI

4-8-01 1

10 1

8-9-OI

8-9-01

8-9-OI

'•♦ .

4-«-!^*'ctr

-I0-02

-I0-O2 1

-I0-02 1

-7-02

.7-02 !

-7-02

-10-02

—

Description.

Cone, jute insulated, lead-
sheathed, armoured, direct
in ground
' Cone. V.B. insulated, laid
solid in iron trough with
iron eover, designed for
5,000 volts, worked at
2,000 volts

Cone, jute insulated, V.B.
sheathed, laid solid in wood
trough with No. 10

Cone, paper ins. V.B.S., laid
solid in iron trough with
tile eover, W.P. 5,000 v.

112 lb. No. 16 S.W.G., eop- [
per ; wound without iron j

Coneent. paper insulation \
V.B.S., laid solid in iron [
trough with tile eover, !•
working pressure 5,000
volts J

See Note (i.) at foot

Length.
Yards.

2,100

7,290

2,440

2400

6,340

21,660

Notes:— (i.) Cable No. 12 consisted 01* Cables Nos. 9, 13

type as No. 10.
(ii.) Worked out result of Curves E, F, and G pi
(iii.) Thomson wattmeter used in series with Swii
(iv.) No wattmeter used in E.xperiments 15 to 21.
(v.) The Swinburne wattmeter with original fine

Nos. 2, 3, 10, II, 12, 13.

Bl.^'S-

.by^%VaU«^y OsciUo-
and -vsTattmeiet
tcr. ^

grapb-

fWattmeter ™

74
lO
520
520

,600
,110
5,205
2,230
2,090 \

1,535 1
i,3»o ;

5i56o ,

18,740

I3t530

1,920

25,650

12,000

3,970
12,160

30
49
25
635
830
866

834

923

112

33
Calc.

17»

610,

83fi
7*

0*020
•029
•017
•098
112
126
•112
•130
•023
•030
•025

•073
024

Oilc.
•032

0090

no
•033

•0315
0127

•0175

•0106

•083

•080

•078

•074

Corre«ponding
Curves.

Applied volts
as Curve 12,
Sheet B
1 1 Current wave
/ not taken
B
As Exp. 5
A
C

f Applied volts
i- as Curve 12,
I Sheet B

E
F
G

L
H

Remarks.

Ironless choker in parallel
Cable alone
Choker in parallel

Cable alone

Choker in parallel
Cable alone
Choker in parallel

Ironless choker, no cable

Oscillograph voltage strip
only calibrated. Watts
worked out from curves

- and the measured R.M;S.
values of voltage and cur-
rent. For I, J, and K
neither strip was calibrated

Sine curves equivalent to E

=^1,650 y^same type as No. 9, and No. 13 = 1,640 yards of same

aU. >^o. 14

Sw\t\bume, w^^num variation of 10 per cent.

^ and 9'

was ws<coil rewound with No. 26 S.W.G. wire in Experiments

^ci

LOSSES IN ELECTRIC SUPPLY SYSTEMS. 717

i peaks, it is impossible to work out the watts even with approxi-
' accuracy. A horizontal difference of 'oi inch in the relative
on of one of the peaks of the curves of current and volts will
alter the power-factor indicated.

it had been possible to obtain photographic records some im-
nent in accuracy would have resulted, but as it is, with curves
by hand, very little reliance can be placed on the worked out
er-factor of the very peaked waves.

)n the other hand, simpler wave-forms can be worked out fairly
rately; Curve D for example. Referring again to the table, it
be noticed that very great discrepancies occur between various
of readings on the same cable and also between the results
ined with the choker in parallel with the cable and without it.
former results should be the more accurate, owing to the higher
jwer-factor.

I Such figures are not very conclusive, but they have been obtained
hh all proper precautions, and it is hoped that some explanations of
le discrepancies may be suggested.

Part of the differences may be due to the effect of alteration
f wave-form (i) on the actual losses, and (2) on the instrument
kiications.

J It has not been definitely proved whether the power-factor of a

ble is altered by alteration of the wave-form of the applied voltage,

not On the whole, it may be inferred that it is altered to some

tent, but not largely. With wave-forms as in curves E, F and G, the

wer-factor for a long paper-insulated cable comes out at about 0*014

Lveraging the three, and with curves H, I and J for the same cable and

approximately the same voltage it is o'o8. A wattmeter was not used in

this case.

This enormous difference canpot be put down wholly to the
difference of wave-form, but is most probably due to the inaccuracy in
working out the very peaked waves of the first set of curves, and the
agreement of the three is probably more coincidence than anything
else. The value obtained from the la^t three curves has been taken as
the more probably correct.

With regard to the effect of wave-form on the other instruments
used, it is stated by Benischke that there may be a difference of 10
per cent, in the readings of electromagnetic instruments with flat and
peaked waves.

In calibrating the various instruments used, differences amounting
to about 5 per cent, were found when using different wave-forms,
the sub-standard being a Siemens Dynamometer with practically' no
metal parts in the frame, and this should read sensibly the same for
different wave-forms and frequencies. The Thomson Ammeters read
higher on the smoother waves. In working out the experiments the
calibration with the particular wave-form of the experiment was that
used. In Table III., giving the wattmeter constants obtained at
different times, the form of wave is noted for each set of readings.
It was found that the voltage across the terminals of the current
coil of the Swinburne Wattmeter (using the fine wire coil) varied in the

718 CONSTABLE AND FAWSSETT : DISTRIBUTION [Mar. 12th,

ratio of about i : 3 in the various experiments owing to the difference
in the current frequency.

It is difficult to say to what extent a wattmeter may be relied on
when the current has about double the frequency of the applied
voltage.

In order to overcome the difficulty of very small scale readings on
the wattmeters, the current coils were in most cases heavily overrun, a
short-circuiting switch being put in except when taking readings.

It is interesting to note that in one experiment, not recorded in the
table, the wattmeter gave a higher reading when short-circuited than
when the current coil was in circuit, no doubt due to currents induced
by the voltage coil, which was in circuit.

In all the recorded experiments the measuring .instruments were
placed in the earthed outer of the cables, as it was found that the
readings were practically identical with those obtained vvith the in-
struments on the inner, and the safety of the arrangement was much
greater.

It was considered a matter of interest to find out how the wave-
forms and values of current and voltage, varied at different points in
the length of a cable, if at all. An experiment was, therefore, made as
follows : —

Six long cables were joined in series, and readings of current and
voltage and tracings of the wave-forms were taken at each end and at
the junction of the two middle cables. Four ends being accessible at
the power-station, it was not necessary to move the oscillograph at all.

The readings taken at the end at which the voltage was applied are
recorded in Experiment No. 12, Table IV., as are also the lengths and
sections of the various cables.

The results of this particular test showed that, contrary to the
authors' expectations, there was no observable difference, either in
the voltage, or in the wave-forms of the voltage and current at the
three points. The middle point was at the junction of Cables
Nos. 10 and 11.

The current, of course, had different values at the three points, but
whether it and the watts were in proportion to the equivalent length of
cable cannot be stated with certainty, as the cables are of different
types and sizes; the main point, however, is that there is no change
in the voltage at the ends of the cable or in the shapes and relative
phases of the voltage and current waves.

This experiment was made under different conditions : (i) with the
cable open-circuited at the far end, and (2) with a small non-inductive
load at the end. The results were the same in both cases except for
a very slight reduction in the "kinks" in the voltage curves in the
latter case and a slight shifting of the current wave owing to the higher
power-factor.

The result is the more remarkable as it is the generally accepted
view that in all long cables there is a rise of pressure due to the
capacity ; and, under certain conditions, this does undoubtedly take
place. In all probability a variation of frequency would have produced
the result expected.

^£W

rjoji^

^ YORK

BRARY

fELNOX

OATI0N8.

FORMS IN CABLKS,
(See Tahle IV.)

\ i

■ 1^

^ 1

1 .

\ 1

/iv

/ 1

— -

fhv s;^1nt*» iH' ''^^^' ''^ '^'^''^^

1903.]

LOSSES IN ELECTRIC SUPPLY SYSTEMS.

719

It is unnecessary to show the curves obtained at the three points, as
they are all practically alike.

The actual readings obtained are given in Table No. IV a.

TABLE No. IV A.
Variation of Current and Volts along Cable.

Volts.

Current

Volt
Amperes.

Watts by
OsciUograph.

901
1>

Cable on ( Point A (near end)

open < Point B (middle)

Circuit. Point C (far end)

Small (Point A

load < Point B

at end. ( Point C

2,000
2,000
2,000

6-o8

3*97
0

565
375
0-64

12,160

7,940

11,300
7,500
1,280

A wattmeter was not used in this experiment, and the oscillograph
curves for the first reading only have been worked out.

The current and voltage curves in the last case are identical.

In addition to the above experiments, it was sought to confirm the
results by the motor alternator method. The connections of the D.C.
motor were as shown in Diagram No. V., the current being measured

®-

iT'X/ ) (motor)

Diagram No. V.

by a very sensitive differential method, which is clearly shown in the
diagram. The galvanometer was calibrated by adding a small known
cmrent to the motor current and noting the scale deflection ; the scale
was a proportional one.

Whilst this method was applicable to the V.B. cable, giving the watts

720 CONSTABLE AND FAWSSETT : DISTRIBUTION [Mar. 12th,

taken by the cable rather lower than the result obtained by the other
methods, it was found that when the jute cables were switched on less
current was taken by the motor than before, no doubt owing to the
efficiency of the alternator being improved by the alteration in wave-
form. This does not include the increase of efficiency due to the
reduced exciting current, as the exciting current was separately
measured.

This objection could probably be got over by adding an inductive
load at the same time as the cable, and adjusting it until the wave-form
of the alternator was of equivalent shape. This could be proved by
either taking oscillograph waves of the potential, or preferably by con-
necting up a condenser (another cable might be used for the purpose)
and adjusting the inductive load until the current flowing into the con-
denser was the same as without the cable under test. The inductive
load would be produced by an air core choker, and could be calculated
and deducted from the total increase in power taken by the motor.
Owing to lack of time, no definite results were obtained by this method.
The motor alternator experiments are of value, however, in showing
the great difference between the V.B. cable and the others.

The improvement in efficiency, apart from the reduction in
exciting energy, caused by connecting circuits having capacity is
a factor to be reckoned with when condemning the wastefulness of
high-pressure cables.

TABLE No.iiV.

Effect of Capacity on Exciting Current.

Exciting

Watts saved

Approx.
Watts in

VolUgc on Cable.

Current with-

Current with

out Cable.

Cable.

Excitation.

Cable (Paper)

10,000

5-8

426

2,000

i 5,000

5-8

142

52^

( 2,000

5-8

5*4

r 10,000

17-5

13-2

555

2,000

\ 5>ooo

17*5

i6'o

193

500

( 2,000

17-5

172

A— 30 K.W. Alternator. B— 120 K.W. Alternator.
Note : — In addition, there is a further improvement in the efficiency
of the Alternator, due to the effect of the altered wave form on the
armature losses.

Table No. V. gives the reduction in excitation energy in various
cases, and it will be noticed that the saving is quite comparable
with the loss by dielectric hysteresis ; so that beyond the objection to
running a larger generator than is required to supply the actual watts
consumed, there is really no great loss due to the use of high-tension
cables, at any rate at 2,000 volts. In the summary, however, dielectric

1908.] LOSSES IN ELECTRIC SUPPLY SYSTEMS. 721

hysteresis losses are included, as exciting energy is not considered in
this paper.

The effect of variation of voltage is shown in experiments No. 15-20.
It will be seen that with the particular form of wave applied the current
increases rather more rapidly than the voltage, and the watts rather
more rapidly than the voltage squared. This, of course, means that
with very high voltages the watts absorbed may be a formidable quan-
tity ; but at the same time it must be remembered that as the voltage
increases, so does the thickness of the dielectric. The capacity is
therefore less, and, assuming no resonance, the cable volt -amperes and
the watts absorbed will by no means increase as the voltage squared.

Some experiments were made on the effect of frequency, and the
power-factor does not seem to be largely altered. As, however, there
was some doubt as to the accuracy of the instruments employed in these
tests, the figures are not here recorded.

The effect of load on the cable on this loss has not been satisfactorily
investigated. It implies taking the difference of two very large quan-
tities, compared with the loss, and is therefore not susceptible of much
accuracy. In any case, the time during which the feeders in a lighting
station are loaded is so small a fraction of the whole time they are
running that the difference in the total result cannot be large.

Taking a comprehensive view of the above results, there appears to
be no doubt that in the case of the V.B. insulated cable. No. 7, the
power-factor is of the order of 0*12, that of the jute-insulated cables
about 0*025, ^^^ of t^® paper-insulated cables something of the order
of 0*032 and o'o8 respectively for Nos. 10 and 1 1 ; the first three results
are fairly consistent with all the statements made in the discussion on
Mr. Mordey's paper. The V.B. cable appears to be an exceptionally
bad cable from this point of view, and the 5,000-volt paper cables
appear to have ^ larger dielectric hysteresis loss than the jute
cables.'

It is noteworthy that the cable which shows an abnormally high
power-factor, viz.. No. 7, is laid in an iron trough with iron cover.

It is possible that this iron trough, completely surrounding the cable,
accounts to some extent for the high power-factor.

Where the cable is in an iron trough with a tile cover, as in the case
of Nos. 10 and 11, the power-f actor is also higher than would be ex-
pected from the type of cable. All the cables in Exp. 12 have the
outers of slightly larger sectional area than the inners — roughly, 5 per
cent, to 10 per cent, larger.

The fact that an external field exists round these cables is proved by
the humming noise produced in the telephones connected to pilot wires

' The thickness of the dielectric between conductors of cables No. 7, 10, 11,
and 13 is 0*28 in. The thickness over the outer is O'lo in., except for No. 7,
in which it is 0*25 in.

The iron trough in which the cables are laid is approximately 3J in. by
3j in. outside and i in. thick.

Cable No. 4 is armoured with steel tape, but the thickness is only about ^ in.,
and the^outer and inner conductors are of the same section.

The capacity of the V.B. insulated cable is abnormally high, being over
hrce times that of a similar paper cable.

722 CONSTABLE AND FAWSSETT : DISTRIBUTION [Mar. 12th,

laid parallel and close to the cables. That this noise is not due to
leakage entirely is shown by the fact that it is slight during times of no
load, and very loud at times of heavy loads. Public telephone cables
along the same route, but further away from the lighting cables, are
not appreciably affected.

Taking the values given above, the total hysteresis loss in the
Croydon system of mains comes out at about 17,000 units per annum,
and is approximately equally divided between the four quarters. This
is not so large a loss that it is worth while shutting down feeders for the
period of light load to reduce it considering the risks involved in so doing.
It is most important, however, to decide on a dielectric which will not
give an abnormal loss, as in the case of Cable No. 7.

Transformer Losses.

The next point to be considered — and it is one of more importance
than losses in the cable dielectrics — ^is that of transformer losses in an
alternating current supply.

TABLE No. VI.

Transformer Losses.

Maximum Load supplied 1,250 k.w.

Maximum Tranformer k.w. in use i»790

Minimum Transformer k.w. in use 920

Total losses during time of heavy load 88,800 units per ann.
^ , Total losses during time of light load... 31,200 do.

Total losses per annum ... 173,200 units.

September
June Quarter. and March December

Quarters. Quarter.

Note : Period (a) is as follows ( 8 p.m. to 5 p.m. to 2.30 p.m. to

(12 midnight. 12 midnight. 12 midnight.

„ (6) „ ( 12 midnight 12 midnight 12 midnight

( to 3 a.]

m. to 5 a.m. to 2.30 p.m.

to 5 a.m. '
8 p.m. 5 p.m.

Table VI. gives the annual losses in the transformers necessary to
deal with 1,250 k.w. output at the Croydon station. These transformers
are placed in 26 sub-stations scattered over the district, and the total
number of 56 of 1,790 k.w. total capacity is made up of : —

2 — 100 k.w.
19 — 50 k.w.
26 — 20 k.w.

3—27 k.w.

6 smaller sizes.

903.]

LOSSES IN ELECTRIC SUPPLY SYSTEMS.

723

These are all in use at times of full load, and the number does not
include spares. The loss is cut down as far as possible by switching o£E
transformers not required for load. An attendant frequently visits the
sub-stations for this purpose.

Notwithstanding this method of securing economical working, the
aggregate losses are very large.

If all the transformers were kept on continually, the additional core
losses would amount to 40,000 units at least per annum.

As an attendant must in any case visit the sub-stations, the saving by
this method of working is very considerable.

The losses given in the table are as nearly as possible the average
losses in ordinary working. The core loss in a particular 100 k.w.
transformer, however, was 979 watts as minimum, with an applied
voltage wave as shown on Curve No. 19, Sheet B, and 1,078 watts as
maximum, with a wave as shown on Curve No. 8, Sheet C.

As this difference is so considerable, it was of interest to investigate
the variations of wave-form occurring in ordinary working throughout
the twenty-four hours. The results obtained are most striking, and very
different to what were expected.

The curves obtained serve to emphasise what is often not fully
realised, namely, that the wave-form obtained from any given alternator
is almost as largely dependent on the kind of load it is called upon to
carry as upon the design of the alternator. The curves were traced on a
Duddell's oscillograph, and the main connections made to obtain them
were as shown in Diagram No. VI., and were such as not to alter the
normal running conditions to any appreciable extent.

Diagram No VI.

LB is the live bus-bar and EB the earthed bar, the system of supply
being 2,000 volts with one pole earthed. Di, D2, D3 are the alternators ;
Fi, F2, F3 are the feeders ; Ri is a non-inductive shunt carrying the
whole current, and R3 and R4 are non-inductive resistances used as a
potential divider to reduce the voltage from 2,000 across the bus-bars
to the necessary 2 volts on the oscillograph ; it consisted of a bank of

}

724 CONSTABLE AND FAWSSETT: DISTRIBUTION [Mar. 12th,

lamps with a small non-inductive resistance, R4 in series with it, across
which the oscillograph voltage strip was connected ; Ri consisted of
brass condenser tubes arranged non -inductively, and tested for absence
of self-induction. The height of the current waves was adjusted by
altering the value of the shunt, and also by means of an adjustable
resistance R2, in series with the oscillograph current coil.

The curves are sensibly correct in shape, but there may be slight
errors due to their having been twice traced. There is also noticeable
a slight difference in the horizontal width of the two half periods, due,
no doubt, to a slight want of uniformity in the rotation of the mirror of
the instrument. This error can, however, be allowed for.

TABLE No. VII.
Variation of Wave Form during 24 Hours.

R.M.S. Values.

No. of

Curve,

Sheet A.

Time.

Machines
Running.

Remarks.

Bus-bar

Total

Volts.

amperes

P.M.

3.40

2,090

Transformers all on.

4.10

2,090

5»7

4.15

2,090

1 10

5,7

4-30

2,090

210

4,5»7

445

2,100

350

i>4i5>7

Some arcs on.

5.5

2,100

505

h 2, 4i 5i 7

( All arcs on (150 amps.
( for arcs.)

540

2,110

534
558

1,2,3,4,5,7

6.50

2,110

1,2,3,4,5,7

Maximum load.

9-5

2,100

340

4,5,7

9.15

2,100

310

5,7

Some transformers oflF.

1 1.5

2,100

215

5,7

"•35

A.M.

2,100

170

12.30

2,080

124
118

3,4

H.N. arcs off.

( I Transformer in each

( Substation on only.

2.10

2,070

3,4

4.50

2,070

103

3,4

6.3

2,070

114

3,4

2-^5

2,070

130

3,4

Some A.N. arcs. off.

2-^

2,070

3,4

All arcs off.

8.25

2,070

8.45

2,070

N.B. — ^The P.D. waves are all to the same scale, but the current
waves are to different scales.

Sheet A gives the curves obtained on January 20th, 1902, and Table
VII. is the key to the reference numbers. Sheet B gives the curves
obtained on July 26th of the same year, and Table VIII. is the corre-
sponding key. Sheet C gives the voltage wave-forms of the various
alternators 'running light, and also some miscellaneous waves, and

SG TWENTY-FOUR HOURS.

P.O Current

dK,

1903.] LOSSES IN ELECTRIC SUPPLY SYSTEMS.

TABLE No. VI IT.
Variation of Wave Form during 24 Hours.

726

No. of
Curve,

Time.

Bus-bar

Total

Machines
Running.

Remarlcs.

Sheet a

VoIU.

Amps.

6.50

( All transformers on.
( 5,000 volt cable on load.

2,070

7.25

2,075

7.50

2,080

140

6,7

8.12

2,100

260

5,6,7

All arcs on.

8.58

2,115

510

5,6,7

Maximum load.

10.50

2,100

310

5,7

11.30

2,100

200

12 mdnt

2,090

IIO

^H.N. arcs off.

12.15

2,090

1 10

4,7

I a.m.

2,090

100

Only a few transformers on.

2.55

2,060

3-32

2,060

Some arcs off.

4-5

2,050
2,060

All arcs off.

7-5

5,000 volt cable off.

7.10

2.060

„ „ „ on.

10.50

2,060

1,3

„ „ „ „

11.20

2,060

„ „ „ „

2,060

( 5,000 volt cable on and

415

) Rect. Arcs Circuit.

*i9

640

2,060

1 5,000 volt cable and all
( transformers on.

7.30

2,060

„ „ 1, ,1

* This current ciure was actually taken before No. i, and the volt
curve interpolated from previous records.

N.B. — ^The D.P. waves are all to the same scale, but the current
waves are to different scales.

Table IX. is the key to this sheet. The sine waves equivalent to the
various voltage waves are shown by dotted lines. The normal periodi-
city is 60 per second.

The curves have not been taken at regular intervals of time, but only
when, owing to some alteration in the kind or magnitude of the load,
there was likely to be a change in the shapes of the waves.

The alternators are all of the iron core, slot wound, revolving arma-
ture type, with large percentage regulation. Nos. i, to 5 were designed
to be short-circuited with impunity. They are direct-coupled to their
engines and, under normal conditions, run perfectly in parallel at all
loads.

On comparing the two sheets A and B, the first noticeable point is
the remarkably peaked waves in B. The only difference was the
addition of a feeder working at 5,000 volts and 3-6 miles long, a few
other 2,000- volt and 200- volt cable extensions, and also No. 6 alternator.

The effect of this increased capacity is to totally alter the shape of
the current waves and to appreciably alter the voltage waves.

726 CONSTABLE AND FAWSSETT : DISTRIBUTION [Mar. 12th,
TABLE No. IX.

Alter-

Description of Curve

nator

R.M.S. VoUs.

No.
M.A.

' I P.D. Curve 30 k.w. Motor-driven Alternator
1 running light

2,060

2 M ), 120 k.w. Alternator running light

t»

3 1 »» »» »f »i i> >» >»

4 1 »» »» »f M f» »l M

„

5 ' »» »» 25^ » f» »f >»

6 ' »» •! »» >» f» »• M

»f

»» .» 500 ». If M »t

(P.D. Curves of Rectifier, Applied and)

' Applied : 2,080
(Rectified: 168

Rectified volts, Rectifier running on small \
Transformer loaded J

...

P. D. Curve 500 k.w. Alternator running light

2,090

»» »» »» »» »» »» »»

t»

„ „ Nos. 6 and 7 Alternators in)

2,090

parallel ; synchronising cur- ■

...

Current about

rent curve dotted

15 amps.

( V i» 30 k.w. Alternator running light )

1 at 15-3 r\J , on 5,000 volt I

...

1 cable through 200 volts — "
V 2,000 volt transformer
P.D. Curve of 30 k.w. Alternator loaded to

2,045

16 k.w. running at 60 rvj , on 5,000 volt .
cable alone )

...

2,050

Current Curve, 30 k.w. Alternator light at
30 r>j , on 5,000 volt cable

...

Current: 0*58 amp.

P.D. Curves of Primary and Secondary)

( Primary : 2,100
I Secondary: 5,250

volts on 2,000 — 5,000 volt 100 k.w. I
transformer J

...

Note :— All the Alternators have slotted iron cores, revolving armatures
and laminated poles.

It is interesting to notice how, with the load consisting chiefly of
cables, the current is leading. As the load increases, the current and
voltage Waves approach each other in phase and the irregularities are
smoothed out. Late at night when the load is mostly arc-lighting, the
current lags. Some very remarkable effects are produced by the flat-
topped wave of No. 7 alternator, as shown in Curve No, 12, Sheet A,
and Curve Nos. 7, 8 and 9, Sheet B.

On Sheet C the additional curves are exceptional, and show what
remarkable effects may be produced by suitable combinations of capa-
city and inductance. These were obtained with the ordinary plant of
the station in the course of some miscellaneous experiments, and they
point out the necessity of not allowing abnormal conditions to ariSe in
working, or the safety of the cables and transformers may be seriously

VARIATION OF VOLTAGE AND CU

She

1903.] LOSSES IN ELECTRIC SUPPLY SYSTEMS.

727

VOLTAGE WAVE FORMS OF ALTERNATORS, ETC.

Vol. 82.

3HPET G (SEK Table No. IX.).
48

728 CONSTABLE AND FAWSSETT: DISTRIBUTION [Mar. 12th,

endangered. Curves Nos. lo, ii, and 12 on this sheet show respectively
the voltage curves of alternators Nos. 6 and 7 running singly and also in
parallel. The dotted curve in No. 12 represents the synchronising
current flowing between the two machines, its R.M.S. value being
about 15 amperes. The voltage curve of the two in parallel is prac-
tically the mean of the separate curves. In connection with the
general question of parallel running of alternators, the following result
is interesting : On one occasion an attempt was made, for convenience
in practical working, to join up two machines in parallel through two
concentric cables, each about four miles long. Under these conditions
the machines would not keep in phase at all, although under normal
conditions they ran perfectly together.

Meter Losses.

The question of meter losses now remains to be dealt with.

There are in use in the district being considered rather more than
1,200 meters, and the same number of Wright's Demand Indicators.
About 1,000 of these meters are Thomson meters, and the rest of the
Westinghouse Co's manufacture.

The shunt losses are by far the most serious, as these go on con-
tinuously, and they amount to a total of 37,400 units per annum.

As is well known, the shunt loss of a Thomson meter is rather high ;
the Westinghouse meter, however, only takes about i watt in the
shunt.

The series coil losses, worked out from the load curves for private
lighting, only reach a total of 1,350 units per annum for both meters
and demand indicators. This low figure is due to the short hours the
meters have any appreciable load on them, and to the fact that in the
majority of cases the meter is never run at its rated full load.

In fact, the total amperage of meters installed is about 3*6 times the
maximum current used for private lighting.

It is evident that a large economy could be effected by abolishing
the shunts altogether and using ampere-hour meters. The only difficulty
is the variation of the consumers' pressure from the supply standard.

In very few cases, however, is the variation more than the limit of
inaccuracy allowed in the meters, and on the average the standard pres-
sure will be very nearly kept to.

Using an energy meter, the consumer who gets a good pressure
pays a little more for his ampere-hours than he otherwise would, and is
well satisfied. In the case of an ampere-hour meter, the consumer with
a bad pressure pays for rather more units than he uses, but he will not
notice the difference in his bill, and he will complain of the bad light
in any case.

There are further advantages in using ampere-hour meters, viz.,
cheapness, ease of installing and less risk of breakdown.

The large loss in the shunts given above is due, of course, to the
particular type of meter in use, but the Thomson meter is not the worst
in this respect, though it is far from being the best.

So far, the losses have been enumerated without much reference to

1903]

LOSSES IN ELECTRIC SUPPLY SYSTEMS,

729

o P ^

2 IS. «

'"* ^ '2 3: 5 i^

R{^

as.

: :

i"i

: = :& ::l ::&in § ^1

M m «o ^ m

I^I^TlTlT: 7: 7: : :

§§

•■■:?••■$■ -^ R i * C "

M F. r>. ih -o

888 8 8 as

»n ^« :o^:oo*:::: : ::
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: : : •* : : '*• : : -^ c^

' ' S^ ■ '5 * ':? ^

<o"oe" • tCiC • N • • •

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8 S 8 *"

i»0 rO i>^ ^

5- ^ a ;?:

...I ::l ::^§ S§ § l§

a 5

X :0

:2 !J

■'• • -J

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■5 "S

'Ji : Q

•S J ?f o2 |ji

^S S ^ ,«>

<5 *^ ^ V o 9.2 *-

(T «B g

730 CONSTABLE AND FAWSSETT : DISTRIBUTION [Mar. 12th,

O
1-1

lA.

kz^

it
1

gga

§si

a:
tj

«1
-

«^

{

1 ^

\ s

i*^

1 ^

I**

:i -

■^

ONN

J3d

INO-i

oniM

19W.] LOSSES IN ELECTRIC SUPPLY SYSTEMS. 731

the total output of the station. In Table No. X. the whole of the losses
are summarised and expressed as percentages of the total units gener-
ated and the total units sold.

Diagram No. VII. is a graphic representation of the losses as they
occur in the system.

It will be seen from the Table that the calculated loss is 22 per cent,
of the units sent out of the station. From the actual sum of the con-
sumers' meter readings, however, the loss appears to be only 18*4 per
cent. This difference of 3*6 per cent, is no doubt partly due to a
rather liberal estimate of the losses in some cases : numerous approxi-
mations are required, and it is impossible to calculate the losses with
great accuracy. It may also be partly due to small errors in the meters.
The total units generated depend on the average accuracy of seven
meters, whilst the total sold depends on 1,200— a difference of 2 or
3 per cent, may thus easily occur.

There is a further side to the question which, however, as it hardly
comes within the scope of this paper, will be briefly dealt with. It
may be economical to waste energy as long as interest has to be paid on
borrowed money. It is, of course, possible to reduce C'R losses at any
rate to a negligible amount, by putting in enough copper, but it is not
economical to do so.

It is the duty of the engineer to design a system which shall give
the best result for the least annual expenditure ; he must avoid losses
in transmission up to the point where the expense of avoiding them
becomes greater than the cost of the energy lost. A case illustrating
the comparative advantages of two alternative schemes is the
following : —

A certain portion of the district considered in this paper was origin-
ally supplied with alternating current from four sub-stations, fed at
2,000 volts. After a few years the load became much heavier than at
first, and it was found both more economical and advisable for other
reasons to change the supply to direct current without transformation,
using the sam« low-tension mains, instead of adding to the section
of the existing cables. The total losses per annum under the old
system amounted to 49,100 units. With the new system for the same
load the losses are 40,300 per annum, so that there is a saving of 8,800
units in favour of the direct-current supply, and the cost of the altera-
tion was considerably less than that of the other alternative.

The average distance of these sub-stations from the generating
station is 1,290 yards, or about three-quarters of a mile, and the maxi-
mum load is about 400 k.w. in all.

With regard to the means for reducing the losses in general to a
minimum, the methods to be adopted have been mentioned under the
various sections of this paper, but they may be summarised here.
Primarily good design is necessary ; after that, care must be taken to
remove useless causes of waste during times of light load.

The cure for waste of energy in switchboards and station connec-
tions is simple design, good workmanship, and choice of suitable posi-
tions. Cable losses may be reduced, assuming suitable dielectrics have
been selected, by switching off high-tension cables not required for

732 CONSTABLE AND FAWSSETT ; DISTRIBUTION [Mar. 12th,

load, but, as in most cases the saving by doing this is small, the extra
risk of cable breakdowns more than counterbalances it.

C»R losses in the low-tension system may be cut down by inter-
connecting the network so as to use all the copper laid down, to the
best advantage. Fuses between the various sections must be relied on
in case of breakdown if this is done.

Transformer losses during light loads are, of course, reduced by
switching out transformers which are not necessary. This practice is
not, in the opinion of the authors, detrimental to the safety of a well-
made transformer. It may certainly pay in some cases to scrap trans-
formers of an old and wasteful type, rather than to use them until they
are worn out. It may be worth while to either artificially alter the
wave shape during the day, or to run machines with a peaked wave in
order to reduce the core loss.

It is hardly admissible to alter the frequency unless no motors what-
ever are in use.

To remove the largest source of loss in meters, shunts should be
abolished, as discussed in the section on meters.

Although this paper deals with the Croydon system of distribution,
the arguments hold good generally, whether the supply is by means of
alternating or direct current.

The question of losses in tramways or power schemes is consider-
ably modified, however, by the altered conditions of working.

There are in such cases only a few hours of light load instead of the
larger part of the day, and as the losses will be practically all C"R loss
in the cables, much heavier copper must be put in to secure the most
economical working.

The losses detailed in this paper are incurred in a system which is
indisputably, on the whole, well arranged and economically worked.
The district has the disadvantage of being a very extended one, so that
the number of consumers per mile of mains is small. This accounts for
part of the large C"R losses, but even so the remainder is of very con-
siderable magnitude, and there must be many supply systems working
under worse conditions.

The engineers of these systems will, however, probably feel hurt if
they are told that they are guilty of slowly, but surely, throwing away
the coal resources of the Empire, and that they are, therefore, neither
serving their profession or their country in the highest degree.

In conclusion, the authors wish to heartily thank Mr. Minshall for
his help and many suggestions, and also to thank his successors at
Croydon for their kind permission to complete the necessary experi-
ments and to publish these results. Several members of their staff
have also merited thanks for much valuable assistance and unflagging
interest in the experimental work. A tribute is due to Mr. Duddell for
having placed on the market so beautiful an instrument as his oscillo-
graph ; but for the interest attached to the use of this instrument, this
paper would not have been written.

1908.] LOSSES IN ELECTRIC SUPPLY SYSTEMS. 733

INDEX TO TABLES.

Description. Table

No.

Losses in Switchboards and Connections I.

CR Losses in Cables II.

Wattmeter Constants III.

Results of Cable Tests IV.

„ Tests on Cables at various points IVa.

Reduction of Exciting Energy due to Cables V.

Transformer Losses VI.

Key to Curves, Sheet A VII.

ft » f> ^ ••• ••• ••• ••• ••• ••• Vlll.

„ „ ff C ... ... ... ... ... ... IX.

Summary of Losses X.

INDEX TO DIAGRAMS.

Description. Diagram

No.

Load Curves for Lighting Station « I.

Lighting Curve for Public Lamps II.

Connection for Wattmeter Calibration III.

„ „ Cable Tests IV.

„ „ Motor Alternator Tests V.

„ „ Station Wave Forms VI.

Graphical Analysis of Losses VII.

Variations of Bus-bar Voltage and Main Current Waves Sheet A.

ft tt ft ft » "'

P.D. Waves of Alternators and Miscellaneous Wave Forms „ C.

INDEX TO CURVES.

Description.

Curve
Current, Voltage, and Watts, Wave Forms, Cable No. 7 ... A.

„ „ „ „ ... ... £>.

tf ft tt tt No. 9 C.

„ „ „ Ironless Choker ... D.

Current and Voltage Wave Forms, Cable No. 11 at Different

Voltages E, F, & G.

Sine Waves equivalent to Curve E. ' H.

Current and Voltage Wave Forms, Cable No. 1 1 at Different

Voltages I, J, & K.

Current, Voltage, and Watts, Wave Forms, in Experiment

No. 12, Table IV L.

734 CONSTABLE AND FAWSSETT : [March 12th,

Mr. M. B. Field then read an abstract of his paper, entitled "A
Study of the Phenomenon of Resonance in Electric Circuits by the
Aid of Oscillograms " (see abovef page 647), read before the Glasgow
Local Section. '

President The PRESIDENT : I will not occupy the time of the Institution in

complimenting the authors of these papers ; e\'erybody who has looked
at them knows how much we are indebted to them for their labours.

^^'Af°^^^ Mr. Leonard Andrews : Whilst I have been very interested in
both the papers we have listened to, I have only a few remarks to
make on the first one. This question of distribution-losses has been
troubling us at Hastings for some years. Until two years ago
our losses in the summer months amounted to about 50 per cent,
of the units generated. Various alterations were made to reduce
these losses, and last year, during the months of June and July,
they only averaged 27*3 per cent, of the units generated. To roughly
locate these remaining losses we fixed meters in the sub-stations
between the low-tension transformer 'bus-bars and the distributing 'bus-
bars. By this means we were able to compare the units generated, the
units turned out from the sub-stations, and the units metered to con-
sumers. The losses in the high-tension feeders and transformers during
the two months referred to amounted to 16*8 per cent, of the units
generated, and the losses in the low-tension mains and consumers' meters
to io*5 per cent., thus making the total distribution-losses 27*3 per cent,
of the units generated. It appears from Table 10 of the authors' pap>er
that the corresponding losses at Croydon amounted respectively to
20*8 per cent., 9*8 per cent., and 30*8 per cent, of the units generated
durmg the summer months. At Hastings the whole of the high-tension
feeders and transformers are cut ofif shorly after 11 p.m., and are left
disconnected until sunset the following day. During the hours of light
load the supply is maintained through the low-tension network alone,
from one sub-station adjoining the works. On page 16 of their paper
the authors suggest that the dielectric hysteresis losses are insu£Ecient
to make it worth while to cut off the high-tension feeders during the
hours of light load, when the risks involved in doing so are considered.
They recommend, however, that some of the transformers should be
switched off to reduce the transformer-losses. They appear to have
overlooked the fact that the risk incurred in switching transformers on
and off is probably quite as great as switching feeders on and o£F,
added to which it is a risk which cannot be so easily dealt with. If the
feeders and transformers are switched off simultaneously, as is done at
Hastings, some simple cable-charging device can be used for this
purpose, and thus the rise of pressure in both feeders and transformers
can be prevented. That rises of pressure do often occur when a trans-
forijier is excited, either from the low-tension or high-tension side,
may be seen by the aid of an oscillograph or by connecting a spark
gap across the primary terminals. If the spark-gap is adjusted to just
not break down at double the normal working pressure of the primary
of the transformers, a spark will jump across the gap at the moment
of connecting the secondary windings to a low-tension source at normal

1903.] DISTRIBUTION LOSSES : DISCUSSION. 736

pressure. Quite apart from the reduction of dielectric hysteresis Mr.Leonani
losses effected by switching off feeders during the hours of light A"****^^
load, there is a great advantage in tmving the whole of the high-tension
system dead in the daytime for alterations or testing. The variation in
the shape of the curves that the authors have shown is very interesting.
We have also noticed that we get a very different shaped curve on
light load to what we get on full load, though this difference only
appears to be noticeable on iron-cored machines. The authors refer
to the fact that they have found that, imder certain conditions, the
current curve lags behind the E.M.F. curve. I have been rather
surprised to notice that at Hastings under no conditions do we get
a lagging current. Even when the load is made up of 50 per cent.
of arc lamps and magnetising current the current still appears to lead.
This is probably due to the fact that there are several miles of vul-
canised rubber cable connected to the system. The authors suggest
that meter losses might be reduced by doing away with the shunt-
windings in meters. I think it would be found that to do this would
tend to introduce another, and a much more serious, source of loss,
namely, that due to the meters failing to start on light load. With
very small meters, that are only expected to carry a maximum load
of two or three amperes, this difficulty does not exist, and it is probable
that with these meters the saving effected by doing away with the
shunt-windings would more than counterbalance any loss due to con-
sumers being supplied at a pressure two or three per cent above the
declared pressure. Larger meters can, however, only be relied upon to
start on light loads if they are constructed with shunt-windings. We
effected a very considerable saving a few years ago by taking out the
whole of our ampere-hour meters and replacing them by watt-meters,
in spite of the losses introduced due to the shunt-windings of the latter.

Major P. Cardew : I will not detain you very long, because. Major
although I made three attempts during the last week to read these
very interesting papers, they were always stolen from me, and I have
not been able to get through them. The point that forcibly occurs
to me, looking back to the time when we were settling regulations,
is how lucky it was that we stipulated that all cables were to be tested
with twice the working pressure with one hour, seeing what a tre-
mendous amount of increase of pressure you get from these exag-
gerated ripples. If that is carried out, I think the cables ought to
stand all that they are likely to be subjected to, even from the amount
of resonance that may take place. There is no doubt that the charging
of a cable is, in all respects, very much like dealing with a live load
on a bridge. I think a practical way to look at it is that the cable
most be strong enough to stand the extra stress which comes upon it.
At the same time, it occurs to me that, with a view to diminishing
to some extent the danger to cables on systems with high pressures,
something might be done in modifying the switching arrangements
—the switching on and off. As far as I have read the discussion
on this paper, and on all other papers, it is always taken that the
al>solute charge — the contact — is an instantaneous thing ; but when
we see what a lot may happen during one period of a fiftieth of a

736

ELECTIONS.

[Mar. ISth,

Major
Cardew.

second it occurs to me that the absolute contact is not by any means
instantaneous, and that the cable is really eased up at high pressures-
pressures of 5,000 volts and upwards — by the arc which takes place as
the switch is closed. And, more than that, we must consider the efiFect
of the closing switch as being to some extent an adjustable condenser,
rapidly increasing its capacity and in series with the capacity of the
cable. That being so, of course the voltage condensed on the moving
contacts of the switch is continually diminishing as the charge
increases ; and, on the other hand, the voltage condensed across
the cable is gradually increasing all that time. By some arrangement
which will give more capacity effect to the switch as it closes, I think
very considerable relief could be obtained.

The President announced that the scrutineers reported the fol-
lowing candidates to have been duly elected : —

Members,
Daniel Coyle. | Joseph Wilkinson.

Associate Members.

Rooke Ainsworth.
Ekiward Calvert.
Samuel McLean.
Charles Andrew Newton.

John Walter Parr.
Charles Norman Robinson.
Walter Stewart.
George Gordon Tomkins.

Associates.

Arthur Baker.

James Stephen Blackwell.

Joseph Boyce.

Thomas William Storey.

William John Charlton.
Thomas Dow Frew.
John Jamieson.

Students.

Charles Reed Allensby.
William George Herbert Cam.
Albert W. Deakin.
William Rowland Ding.
Thomas Ellis.
Reginald Woolton Fowler.
P. L. R. Fraser.
James Frederick Gay.
Alexander Lindsay Glegg.
Masanoske Hayashi.

Kenneth Horton.
William Howes.
Clarence Hambly Hughes.
Alfred James Munday.
Thomas George Partridge,
John G. Potts.
Morgan Howell Rees.
Alfred Ernest Scott.
Frederick Smith.
Richard Edward Wellard.

1903.] TRANSFERS. 787

The Three Hundred and Ninety-first Ordinary General
Meeting of the Institution was held at the Institution
of Civil Engineers, Great George Street, Westminster,
on Thursday evening, March 26, 1903 — Mr. jAMES
Sv^iNBURNE, President, in the Chair.

The minutes of the Ordinary General Meeting held on March 12th
were taken as read and signed by the President.

The names of new candidates for election into the Institution were
taken as read, and it was ordered that these names should be suspended
in the Library.

The following list of transfers was published as having been
approved by the Council : —

From the class of Associate Members to that of Members —

Reginald Page Wilson.
From the class of Associates to that of Members —

Stephen Stewart Goodman.

From the class of Associates to that of Associate Members —

Leonard Breach. I Arthur Frederick Malyon Gatrill.

Edward Macgregor Duncan. | Thomas McGill.
Herbert James Read.

From the class of Students to that of Associates-
Percy Meares Crampton.
Robert Saunders Newton.
Richard Lloyd Pearson.

Messrs. F. Graham and A. G. Inrig were appointed scrutineers of
the ballot for the election of new members.

The President ; The Students have been working very hard, and
have got up a large subscription in aid of the Building Fund. They
have collected no less than £83 6s., and after deducting the various
small expenses, there is a balance of £79 los. 6d. to add to the Building
Fund. I am sure the Institution would like me to read this letter : —

" March 26, 1903,
" Dear Mr. McMillan, — I enclose the balance sheet (which is a copy
of my own) of our Students' Subscription List to The Building Fund of
the Institution of Electrical Engineers. This fund was opened on
January ist and closed on March 30th last, and through our efforts we
have been able to collect, as you will see, a net amount of £yg los, 6d.
By a motion of the Committee, I am not to give you a list showing the
amount subscribed by each student, but just a list of the names of those
who have subscribed ; this Hst I will send you, together with a cheque
for the balance I have in hand, in the course of a day or so. I also

788 ARTICLES OF ASSOCIATION. [Mar. 26th,

enclose a copy of the letter that was sent out, and hope these will
reach you in time to be placed before the Council this evening.
The total number of Students who have subscribed is 644, although
included in this number are some Students who are studying electrical
engineering, though not Student Members of the Institution. My
Committee are extremely pleased with the result of this movement, as it
shows that the Students recognise the desirability of a home for the
Institution.

" Believe me,

" Very sincerely yours,

" Harold D. Symons."

Donations to the Library were announced as having been received
since the last meeting from Messrs. C. Bright, C. Naud, and Whittaker
& Co. ; to the Building Fundy from Messrs. B. Balaji, S. Evershed, and
J. F. Henderson ; and to the Benevolent Fund from Mr. W. E. Russell,
to whom the thanks of the meeting wer^uly accorded.

The President : I have to announce the result of a Special
General Meeting of the members, held for the purf)ose of altering
the Articles of Association. There were not many alterations, and
I will just explain the principal ones. The first is to give the
Council the power, which is given in most Societies, of removing
at their discretion any one who is either a bankrupt, on the one hand,
or on the other hand — the' two things have nothing to do with each
other — a felon. That is a Clause which is inserted in most Articles of
Association. I would point out that it does not by any means indicate
that supposing a man were unfortunately to become bankrupt he is to
be expelled from the Institution, but supposing a man were a fraudulent
bankrupt, or it was supposed that he was a fraudulent bankrupt, it
might be very necessary to remove him ; but unless there is some such
rule as this the Council would not be able to do so without practically
saying he was a fraudulent bankrupt, and that might lead the Institu-
tion into an action for slander, libel, or something of that sort. As the
Article has been altered, in extreme cases it gives the Council
power to take action. The next alteration is with regard to the Vice-
presidents. Under the alteration two Vice-presidents retire every
year. The idea is that it does not follow that every Vice-president
should in the ordinary turn become President. It is rather difficult
under the old rules to elect a member a Vice-president unless you
desire to make him President also, and there are a great many people
who would be very useful as Vice-presidents without necessarily being
very well qualified to serve as President. It also gives us a bigger
number to choose from. The arrangement is that in future two Vice-
presidents will always retire, and the President must be chosen from
some one who has been a Vice-president ;* so that a man who has once
been a Vice-president is eligible for the Chair. By that means we will
get a number of people, as it were, in stock to choose from, and it is
felt that that will be better for the Institution. The only other
alteration of any importance which I think I need mention is that the

1903.] ELECTION OF NEW PRESIDENT. 789

Associate Members are now to have the power of voting with the
Members in any important matter, such as altering the Articles of
Association, or anjrthing of that kind. The Council feel that the
Associate Members and the Members only differ in degree, and that
they ought to be one body. The last alteration is a matter of form,
which, I believe, is legally unnecessary ; it provides that every new
member shall promise to agree to the rules of the Institution, and
so on.

As I mentioned at our last meeting, it is very important that the
Institution should have a President who should not only take charge of
the Institution during the time of the International Telegraph Congress
which is to be held in London, but should also be in the Chair early
enough to make his arrangements for taking over the control of the
Institution during the whole time. I sent in my resignation, as I said
I would, and the Council have elected Mr. Gray to take the place
of President. I can only say that I have the greatest pleasure in
resigning in favour of Mr. Gray. Mr. Gray will now have time to
organise the entertainments of the Congress in a way that I feel sure
you will find will do great honour to the Institution. I have great
pleasure in resigning in favour of Mr. Gray, and I will now ask him to
take the Chair.

[Mr. Swinburne then vacated the Chair, which was taken by
Mr. R. K. Gray.]

Mr. J. Gavey : Gentlemen, before the new President addresses you,
I should like, if you will allow me, to intervene with a few remarks.
The post of President of this Institution confers high honour on the
holder, for he is for the time being the head of our profession. It also
entails very onerous labours, labours of which, perhaps, only those who
are on the Council, or who have served on the Council, are really good
judges. You are able to appreciate the able manner in which the
past President has upheld the high traditions of his office in presid-
ing over your meetings. I, as a member of the Council, can testify
to the great business aptitude with which he has conducted the
deliberations of the Council, and with which he has managed the affairs
of your Institution. Gentlemen, great professional ability or great
business acumen compel admiration, but there are other qualities which
command esteem and regard; and personally I can say that your
retiring President has, during his year of office, shown such an amount
of tact and courtesy in dealing with the affairs of the Institution, that he
leaves behind him a body of men, who, I venture to say, consider them-
selves his personal friends. If you want an illustration of the tact and
courtesy with which he has dealt with his duties, I need only call your
attention to the graceful and generous manner in which he has retired
before the expiry of his period of office, in order that his successor may
have the fullest opportunity of organising the reception of the
International Telegraph Conference in the manner most satisfactory
to himself and to the best advantage of the Institution. I have much
pleasure in proposing a very hearty vote of thanks to the retiring
President.

Mr. W. H. Patch ELL : Gentlemen, the duty which devolves upon

740 CONSTABLE AND FAWvSSETT [Mar. 26th,

me to night should properly devolve upon one of the Vice-presidents,
but they are unfortunately absent owing to the Dinner to Sir William
White, which has called for the personal service of them all. Our past
President — I am sorry to have to call him so so soon— ought to have
been there also, and it is only another instance of the courtesy with
which he has invariably treated us here that he has foregone so much
of the dinner, although he hopes presently to get in for the ices.
Mr. Gavey has told you something about our past President's
handling of the Council, and you have seen for yourselves the way
in which he has handled these meetings. As a specimen of his
tact, I need only refer to the fact that he had hardly got into the
Chair when he had to head the deputation to the Board of Trade, and
I think the handling of that deputation was just a masterpiece of
diplomacy. No words from me could give you any higher opinion of
Mr. Swinburne than he has earned for himself. He is only a young
man, and I hope we may live to see him serve us again when, instead
of having an abbreviated year of office, I hope we may be able to give
him a leap year.

The resolution was carried with acclamation.

Mr. J. Swinburne : Mr. President and gentlemen, it is very
difficult indeed for a man to reply to such very kind speeches as I have
heard to-night, and to reply after a vote of thanks has been carried in
the way in which you have carried this one. I can only say that being
your President is the greatest honour that can be conferred on any
member of the profession. But in my case I have felt that it was not
only a great honour but an immense pleasure. I have had nothing but
pleasure throughout the time I have had the honour of being your
President, I am very sorry to resign in one sense, and in another sense
I am very glad indeed, because, though I have enjoyed my time very
much, and everybody has treated me with the greatest kindness, I
cannot help feeling that in Mr. Gray you have a more experienced
man, a man who will be about the best President you possibly could
have. I thank you, gentlemen.

The President (Mr. R. K. Gray) said: Gentlemen> before pro-
ceeding to the discussion of the papers that we have before us
to-night, I desire to say, in as few words as possible, that I appre-
ciate very much the honour which has been conferred upon me by
the Council, and I sincerely hope I shall be able to follow the tradi-
tions of my predecessors in this Chair. I will not occupy your time
any longer, except to tender you my best thanks for the very kind way
in which you have received the announcement which Mr. Swinburne
has made to you.

Resumed Discussion on Papers on " Distribution Losses in
Electric Supply Systems," by A. D. Constable, A.M.I.E.E.,
AND E. Fawssett, A.I.E.E., and '* A Study of the Phenomenon
OF Resonance in Electric Circuits by the Aid of Oscillo-
grams," by M. B. Field, M.I.E.E., A.M.I.C.E.

Mr. Mr. T. H. MiNSHALL : I think the peculiar value of these two

"* papers which arc before us to-night, dealing as they do with the

1903.] AND FIELD : DISCUSSION. 741

oscillograph, is not so much the accuracy of the results which are given, Mr.

although many of those are very interesting, but the number of new

suggestions which they make to men engaged in practical engineering.

Mr. Constable's paper, together with the diagrams which are given,

has come in a sense as a revelation to a great many station engineers.

A good many of us did not realise, until the oscillograph was made

a practical instrument, what extraordinary wave-forms we have to deal

with ; and when one sees some of the very peculiar shapes which

are shown in some of the tables, more especially in Table No. 4,

one is not at all surprised at almost any form of resonance effect

or breaking-down effect which one hears of in actual practice. There

are several points that occur to me which have not had much

attention drawn to them before. One of those is the question of the

enormous loss which goes on in all central stations. One does not

realise that actually 25 per cent, of the total output of a station is, at

the present time, lost. Of course it must be borne in mind that of that

loss a great deal occurs at the top of the load, and that hence the cost

of generation of those units must be taken as the maximum possible.

Taking these units given in the paper, and allowing the average

cost of generation of the total of 173,000 units, we get between

£"200 and £'yyo a year actually lost; if you can save them, or

prevent them going in any way, it is all profit. I do not know

that there are any other points that occur to me in connection

with the first part of the paper. The dielectric hysteresis is the

part which appeals to me as the most interesting, although possibly

it is not the one of the greatest practical importance. This paper

originated with some experiments that Mr. Constable made for me

in connection with the discussion on Mr. Mordey's most interesting

paper last year. Members may recollect that in that paper Mr. Mordey

showed some results with a power-factor of the order of o'l. The

Institution at the time as a whole, I think, did not entirely agree with

those figures, and we made some experiments at Croydon to see if such

a thing were possible. It so happened that the experiments we

conducted were not on a paper cable, but on a vulcanised bitumen

cable, and we got results almost exactly agreeing with Mr. Mordey's.

I do not pretend that anybbdy believed them ; so we spent some time

and trouble since then in attempting to produce the results by several

methods. I think Mr. Constable shows here fairly conclusively that

with a cable of this peculiar construction and material, it is quite

possible to get a power-factor of the order of o*i. As a matter of

£act, when he comes to deal with jute cables and paper cables, of

course then the results which he obtained are more in accordance with

those which were obtained by so many investigators last year. There

is no doubt, I think, that the ordinary power-factor of the ordinary

paper cable is of the order of 001 or 0*02. I do not think it would

be very much higher, although some of the jute cables seemed to

go as high as 0*03, but I should think 3 per cent, is the maximum

power-factor which is obtained from any of these cables in commercial

use. Mr. Constable gives on page 713 a very interesting resume of

the various methods \vhich are applicable to a measurement of this

Minshall.

742 CONSTABLE AND FAWSSETT [Mar. 26th,

Mr. kind. It is very important indeed that one should clearly realise the

"****"* great difficulty there is in conducting investigations into what he has
called dielectric hysteresis. The five methods he has given here are all
of them to a certain extent practical, provided that 3rou have sufficient
time and apparatus at your disposal. The first one certainly appears to
be one of the best. When I was in America last year I discussed the
matter at some length with Mr. Steinmetz and Mr. Berg, and they
were of the opinion that they would use the one the authors used ;
but when I showed them some of the wave-forms in the diagrams on
page 711, they agreed that it was not perhaps such a good method to
use as they had previously thought. My own conclusion is that if
it is not possible to use a calori metric method, the only method
on which one could really rely with bad wave-forms is No. 3,
that is, the direct measurement of increased power necessary to
drive an alternator when a cable is switched on. Of course at
the first glance it appears as if the measurement to be made is so
extremely minute that it is impossible to measure it ; but a small motor
alternator, carefully driven, with the supply at the direct-current end
measured on a potentiometer, would enable one, on a long cable, to
get results of very considerable accuracy. The difficulty is that the
wave-form of the alternator itself, unless care be taken, gets altered
during the experiment ; that is to say, you may have practically a sine
wave before you put the cable on, and then immediately you put it on
you get one of the forms shown in Table 4. I know that Mr. Constable
took very great efforts to get over that. He took a motor alternator
and loaded it up with 30 kilowatts, and switched a cable on the losses
in which added i kilowatt extra load, hoping thereby he would
preserve the same wave-form as before. But he found it was
impossible to be quite sure, and I am afraid the results he obtained
from that are more or less negative. If one could get a sine-wave
machine, and potentiometers of sufficient accuracy, it is a method
which promises a good deal in the hands of a really careful investigator.
The author has not drawn attention to one very interesting experiment
which we made some time ago at Croydon to show that the current,
and even sometimes, owing to the alteration in wave-form, the watts
flowing into a cable on open circuit may be actually greater than when
some load is put on at the end. We took a long cable of about
7,000 yards, put on an alternator, and measured the capacity current
flowing into the cable. We then added a couple of transformers,
open-circuited, whose core losses amounted to two kilowatts, the result
being that the current entering the cable was measurably smaller than
before. That has been repeated a good many times, but I do not
think he draws attention to it anywhere here. It merely shows that if
properly arranged the capacity of a cable on a large net work may be
of advantage rather than otherwise. As a matter of fact it is not
actually so deleterious to the supply as possibly is sometimes imagined.
I do not think there are any other points that I remember at the
time in that connection, but I should like to refer to a remark
made in connection with telephones. We had much trouble from
Sydenham and Croydon and on to Purley with the telephone cables ; we

1903.]

AND FIELD; DISCUSSION.

743

were a great nuisance to the National Company, and a great deal more Mr.
nuisance to ourselves. Eventually the manager of the National Tele-
phone Company in that neighbourhood and myself investigated the
matter at some length and came to the conclusion that you can take
a concentric cable, put it in a lead sheath, in an iron trough, and
lay another cable by the side of it also in a lead sheath, and still
get any amount of stray field, or what appears to be stray field : you
can get enough humming to make it practically impossible to hear
on the telephone. Some people say it is leakage, others static effect.
We investigated very carefully to find if it was leakage, but we satisfied
ourselves entirely that it was not electrical leakage at all. When the
current increased in the evening the sound was very greatly increased
too ; in the day time, when there was very little current flowing in
the cable, there was very little noise in the telephone. We came
finally to the conclusion that the only really satisfactory way of
running telephone cables near high-tension cables was not to trust to
any sheathing whatever, but to increase the distance. I shall be glad
to hear the experience of other engineers on that point, because it is
one which caused us a great deal of trouble, I will not detain the
Institution by drawing attention to the number of other uses which the
oscillograph is going to have in the future ; but there is one in
particular which appealed to me, namely, that in specifying high-
tension machinery it is now becoming customary to specify the wave
form of generator, rotary, or motor generator as the case may be. One
has not only to specify voltage, and that sort of thing, but one has to
say what sort of wave the machine is to give. Hitherto it has been
easy to specify, but it has been difficult to see that you were getting
what you wanted. Here you get an opportunity of seeing that the
contractor is complying with a specification, an opportunity which
hitherto has been impossible. I think every alternate-current station
engineer should get his directors to agree that the sum expended on
this little apparatus is very well spent indeed.

Mr. W. DuDDELL : Messrs. Constable and Fawssett have used three
different methods to determine the losses in their cables, viz. : —
(i) The wattmeter method.

(2) I'he wave-form method.

(3) The extra power required to drive an alternator method.
Of these methods I have no doubt that the wattmeter method is one

of the best, if not the best. If a suitable wattmeter and suitable scries
resistances for the pressure coil are used, accurate results can be
obtained, in spite of the wave-forms being as irregular as those shown
in Mr. Constable's paper. I hope that Diagram 4, which shows the
wattmeter connection, is wrong. In it the pressure coil of the watt-
meter is shown connected direct to a resistance marked R4, with no
non-inductive resistance in series with it. If that was really the case,
very large errors were introduced. Judging from the oscillograph
connections, this appears to have been the case, for the terminals of
the resistance R4 are shown connected straight to the oscillograph,
which only requires i volt to operate it.

From the text it seems as if they used some resistance in series
Vou 8Z 49 (Rev.)

Mr. Duddcll.

744 CONSTABLE AND FAW8SETT [Mar. 26th,

Mr. Duddeu. with the pressure coil of the wattmeters which they have omitted to
show. In any case it would be of great interest to know the values of
the resistance, self-induction, and capacity of the pressure coil circuits
for each of the wattmeters they used. I hope the authors will be able
to give these figures, as they will enable a more accurate estimate of
the obtainable acciu"acy to be formed.

Coming next to the methods of calibrating the wattmeters on power
factors less than unity, they state that they calibrated them with a
lagging current by using a choking coil. If the choking coil is properly
constructed, there is not much difficulty in calculating the true power
losses in it. They also state that they obtained a leading ciu-rent having
a power-factor of 0*14. I should like to ask them how they calculated
the value of the power-factor in that case. Diagram No. 3 throws no
light on the matter whatever, and, as far as I can gather, it is impossible
to calculate the power-factor unless they either assume a pure sine
wave, or analyse the actual wave used, and calculate each term of the
series representing the wave-form separately. There is no indication
that this was done. If the actual wave used is that given in Fig. D.,
which is far from being a sine wave, and if they assumed a sine wave
in their calculations, then the calculation of the 0*14 power-factor and
the calibration of the wattmeters with leading currents is inaccurate.
I hope the authors will explain this matter fully in their reply, as it
afiEects the accuracy of all their wattmeter measurements of the cable
losses. I

[Communicated May 6th, The ingenious method described by Mr.
Constable in his reply neglects the self-induction of the fixed coil of his
wattmeter and assumes the current A, through it in phase with the
applied volts V. Was this self-induction negligible compared with the
resistance ?]

Ever since Mr. Mordey's paper, Mr. Mather and myself have been
working on the design of a satisfactory wattmeter and series resistance,
especially for use on very low power-factors, and we have' now designed
and had in use for some months an astatic wattmeter which is quite
free from metal parts in the frame, which has the minimum amount of
metal necessary in the coils, and which gives a good deflection, even
with very low power-factors. In fact, the wattmeter is so sensitive that
with a power-factor of o'l you get a complete revolution of the torsion
head, so that a power-factor of o'oi is perfectly easy to read with a high
degree of accuracy. We have also designed and constructed special
forms of resistances for use in series with the pressure coil, for, as h
well known, the errors in these resistances are very often very much
bigger than that due to the self-induction of the pressure coil of the
wattmeter itself. We have made numerous experiments to test the
accuracy of this wattmeter, and we hope to have the opportunity later
on of describing it and the resistances. With regard to method No. 2,
the wave-form method, it is not very suitable for very irregular wave-
forms, unless the wave-forms are actually photographed. It does not
suffice to photograph a mean wave-form, as Mr. Field has done. You
must get an individual pressure curve and the corresponding current
curve belonging to it, and you must work the result out from the

1903.] AND FIELD: DISCUSSION. 745

contemporaneous values of the P.D. and current obtained from those Mr. Duddcu.
two curves. You must not take the P.D. curve of one period and
integrate with the current curve of the next, nor take a mean of, say,
ten P.D. waves, and work out the power-factor with the mean of ten
current waves ; you must take each individual pair of curves together,
because they may vary considerably, I have on the table the apparatus
I use for obtaining photographic records, which records the individual
waves and not the mean waves, like the apparatus used by Mr. Field.
There are really two sets of apparatus here. One is suitable for
working on voltages up to 15,000 with no earth connection, the record
b€nng made either on a falling plate or on a long length of film up to
about 160 feet where many consecutive wave-forms are required. The
other apparatus is for short lengths of film only.

With regard to method No. 3, the extra power required to drive the
alternator, Mr. Minshall was, I think, a little inclined to advocate this
method. I regret that he has done so, for I totally disagree with him.
I have never been able to find any basis for hoping for accuracy from
this method. The efficiency of the alternator is totally changed by the
action of the capacity current. With ordinary alternators, as I hope to
show you presently on the screen, the capacity may produce serious
resonances of the higher harmonics, and the effect of adding the
capacity current will tend to excite the alternator, and will alter the
efftcicncy by altering the distribution of losses. I see no means of
getting over this objection. In fact, sometimes an alternator seems to
take less power to drive it if the cables are connected, but most alter-
nators seem to take very much greater power, the iron losses being
increased by the high frequency of the capacity current.

Turning to Table No. 4 of Messrs. Constable and Fawssett's paper,
they give the results of the tests of five different cables; by taking
means of their figures their results may be resumed as follows : —

Cable No. 4 power-factor 22 per cent.

II-I „

2-8 „

7*3 and 2*4 per cent

This latter value, 2*4 per cent., was obtained with the choker in parallel,
and is probably the more accurate, as the wattmeter was then working
at a higher power-factor. For the last cable. No. 11, they give two
totally different sets of results. The mean of the first set, obtained from
curves E, F, G, is i'4 per cent., and the mean of the second set, obtained
from curves I, J, K, is no less than 8 per cent. I should like to ask them
what is the difference between the tests E, F, G and I, J, K. In one
case they say they obtained 1*4 per cent., and in the other 8 per cent.
If you refer to the diagrams of the wave form, you will note that the
first three, E, F, G, have a resonance of the fifth harmonic, and in the
last three they got resonance in the third harmonic. How is it with
the same cable they have these two different resonances ? Did they
use a different alternator in the two cases, or different frequency, or
was there by any chance a transformer connected across the cable in
the case of I, J, K ? In no case do they give any indication as to the

746 CONSTABLE AND FAWSSETT [Mar. 3eth,i

Mr. Duddeu nature of the machine and frequency used in each test. There is no
doubt whatever that the self-induction connected between the terminals
of the cable tests I, J, K was very much greater than in E, F, G, if the
frequency was the same ; yet they have accepted the high loss as more
probably correct. Taking the figures for the five cables, which are not
on the face of them doubtful, the losses, as Mr. Minshall said, are
generally under 3 per cent., except in the one case of the No. 7 cable.
That cable appears to be 'a bad cable as far as light-load loss is
concerned.

I have tested by means of the wattmeter already mentioned various
cables belonging to electric light companies in and around Londoiu
and in general the power-factor has varied from 1-5 per cent, to 3 per
cent., the power-factor differing from one cable to the next, even ^when
they were very similar in make and construction. I have also tried the
effect of varying the voltage used on some cables over a fairly wide
range, and find, as Messrs. Constable and Fawssett point out, that there
seems to be a tendency for the power-factor to increase with increase
of the applied potential difference. The effect of a change of the
applied wave-form due to resonance of one of the harmonics has been
to make the power-factor larger when the resonance occurred than when
there was no resonance, evidently due to the increased value of the
maximum instantaneous E.M.F. In all the tests I have so far made —
and they have been made under ordinary working conditions, with the
cables connected up to the switchboards exactly as used, and no allow-
ance being made for any C'R losses due to the capacity current — I have
never come across a cable giving a power-factor above 3*5 per cent,
except the No. 7 cable at Croydon, which I once tested, and I then had
doubts as to the accuracy of my own test, as I stated at the time, as
during the test there appeared to be such a violent resonance that I
could distinctly hear the resistances in series with the volt coil of the
Swinburne wattmeter I was using giving a brush discharge, though the
R.M.S. voltage was only 2,000 volts. I still feel that this No. 7 cable
should be further tested to find out the true cause of the great loss in
it, whether it be real or apparent. Messrs. Constable and Fawssett
suggest that it may be caused by a magnetic field, though this present>
serious difficulties. I asked Mr. Fawssett to make some further exf)eri-
ments on this point, the results of which he will no doubt tell us. The
noise in the telephone referred to may well be due to leakage from the
outer to earth, and would increase with the load.

Messrs. Constable and Fawssett's paper strengthens the conclusion
that it is quite possible to obtain commercially cables with a power-
factor less than 3 per cent., and that therefore the danger pointed out
in Mr. Mordey's paper of the large power schemes being. crippled by
the light-load losses in the cables themselves is not at all serious, and I
would suggest that we may take warning from Croydon and avoid
cables having such absurdly high losses as their No. 7. V.B. cable
appears to have. Taking Messrs. Constable and Fawssett's tests of the
No. 7 cable as correct at a i^. per unit, £^0 per annum of the rate-
payers' money is being wasted in warming the cable instead of a
quarter that amount, and probably ijd. per unit is an under-estimate

J-]

AND FIELD: DISCUSSION.

747

Mr. Duddell.

Fig. B. — Alternator and Cables, Normal Speed.

Fi(i. C. — Alternator and Cables, 8 per cent. Over Speed.

Fkj. D. — Alternators and Cables, 26 per cent. Umier Speed.
Scale': i mm. = 458 volts.

748 CONSTABLE AND FAWSSETT [Mar. 26th,

Mr. Duddeii. of the cost of producing the power. With regard to No. 12 cable,
which I believe includes most of these other cables, if you take the
total losses, 901, you will find it is very little bigger than the 6oi taken
in No. 7, so that how it includes the high losses in No. 1 1 I do not
understand.

Turning to Mr. Field's valuable paper on the resonance question, I
do not think that he has laid sufficient stress on the dangers to the
insulation due to these resonances of the higher harmonics.

Out of four large plants I have recently tested, three suffered
seriously from resonances, and Mr. Field and Messrs. Constable and
Fawssett show us that both Glasgow and Croydon do. These reso-
nances not only strain unnecessarily the insulation of the cables ; they
also reduce the efficiency of the machines, make the regulation bad and
the working of motors difficult.

Before proceeding I will define the term form factor as the ratio

maximum instantaneous value . , i. r 1 ^ *

- ,-r~i^-^ , for any wave-form, a most useful factor

R.M.S. value -^

which gives a measure of the strain on the insulation due to the wave-
form.

I have to thank the Kensington and Knightsbridge Company for
allowing me to show some resonances obtained on their circuits which
will, I hope, exemplify the danger to insulation due to resonances. In
each case the R.M.S. voltage is the same, viz., 5,000. Fig. A is the open
circuit wave-form of the one of their alternators ; the maximum volts
are 1*45 times the R.M.S. volts, or in other words the form factor is 1*45,
about the same as for a sine wave. Fig. B is the P.D. wave form of the
same alternator with some cables connected which were on open
circuit, the alternator running at normal speed ; the form factor is i*67.
If, however, the speed of the alternator increases to only 8 per cent
above the normal, a resonance of the seventh harmonic occurs (Fig. C.)
and the form factor increases to 174. On the other hand, if the machine
is allowed to slow down to 26 per cent, under normal speed, a reso-
nance of the fifteenth harmonic takes place (Fig. D), and the form factor
rises to I •94. This shows that, with a constant excitation, lowering the
speed of the alternator may increase the strain on the insulation. A
cable should never be energised by raising the speed of the alternator
after exciting the latter, for fear of passing through dangerous
resonances ; the alternator should be run up to correct speed first, and
then the excitation should be gradually raised.

In some other stations I have known the form factor to increase to
as high as 2*2 ; thus, supposing 10,000 R.M.S. volts was applied to the
cable, the maximum instantaneous voltage would be no less than
22,000 volts, or, due to the resonance, the cable would be strained with
as high a maximum voltage as is given by a sine wave having a R.M.S.
value of 15,500 volts, so that a cable designed to work at 10,000 volts on
a sine wave might frequently be strained 55 per cent, in excess, due to
a resonance of one of the upper harmonics. I think that cable makers
have in some cases been unjustly blamed for failures due to resonance.
These resonances are a frequent cause of the failure of E.S. voltmeters.
J t is to b^ noted that these high peaks on the P.D. wave mentipoed do

1903.] AND FIELD : DISCUSSION. , 749

not show on the station voltmeter which reads the R.M.S. value, so the Mr.Duddeii.
cn^neer in charge has no idea how serious the strain on his apparatus
is. It will be said that the ordinary rules of testing to twice the working
pressure allows for the above strains. But this is not the case, as the
whole of that margin and more is required to allow for the strains due
to oscillations without its being reduced in any way due to resonances.
I have calculated the form factors for some of the wave forms in
Messrs. Constable and Fawssett's paper : —

Curve A.

189

Curve E.

197

Curve I.

17s

„ B.

1-88

,, F.

1-96

.. J-

172

„ c.

r8o

.. G.

193

.. K.

£•69

,. D.

'•53

„ L.

185

The difference between the form factors of curves E, F, G and of
curves I, J, K, which are for the same cable, No. 11, show, as I h;ive
already mentioned, that the conditions under which these tests were
made were evidently very different.

I think the above values, which are in no way exceptional, show

Fig. E. — Converter ; Effect of Sparking at Brushes on Direct- Current Side.

how very serious the dangers due to resonances of the higher harmonics
are in practice.

Mr. Field has referred to ripples on the D.C, side of a rotary
converter. I should like to draw attention to the irregularities which
sparking at the brushes of a converter may produce in the P.D. wave-
forms on the alternate-current side.

Fig. E shows the two P.D. waves of a small two-phase converter
which was allowed to spark at the commutator.

The irregularities in both the P.D. waves due to this sparking are
very marked. It seems to me that these high frequency ripples might
easily be resonated and lead to very serious difficulties and dangers in
working, so that a converter which was working perfectly satisfactorily
might, by being allowed to spark at the brushes, cause a serious
resonance with the attendant dangers to itself and the rest of the plant.

Prof. A. Hay : In connection with Messrs. Constable and Fawssett's Prof- Hay.
paper, I should like to make a few remarks with regard to the alleged

750 CONSTABLE AND FAWSSETT [Mar. 26th.

Prof. Hay. magnetic field which exists around the concentric cable. It is very
difficult to believe that such a field can exist, and the only way in which
it can possibly be brought about is by a slight excentricity in the inner
conductor of the cable ; a large amount of excentricity is of course out
of the question. It seems to me that the experiments with telephones
prove nothing at all, because there is a much simpler explanation,
namely, a purely electrostatic disturbance. If you consider the outer
conductor of the cable and suppose that it is conveying an alternating
current, you will have a periodic rise and fall of potential at each end
of the cable. You have your pilot wire in the same trough near the
outer conductor, and you are bound to get a considerable amount of
electrostatic action between the pilot wire and the outer conductor of
the concentric cable. Such disturbances are well known to telephone
engineers, and I think that there is no doubt the effects observed are
due entirely to purely electrostatic causes and not to electro-magnetic
disturbances, as has been suggested by the authors. In connection
with the remarks made by Mr. Duddell, I am sorry to note that he is
introducing a new term and using an old name for it. He speaks of
the form factor of the wave-form. As a matter of history, I believe I
am right in saying that Dr. Fleming was the first to introduce certain
terms which had definite reference to the wave-forms of alternating
currents and P.D.s. The two terms introduced by him were the form
factor y which he defined as the ratio of the R.M.S. to the mean value of
the wave, and the amplitude factory which denoted the ratio of the
R.M.S. to the maximum value. Dr. Fleming's amplitude factor is thus
the reciprocal of Mr. Duddell's form factor, and Dr, Fleming's form
factor is something totally different. As the term form factor has been
used by both English and continental writers in the meaning given to
it by Dr. Fleming, I hope Mr. Duddell will try and invent some other
suitable term for the ratio of the maximum to the R.M.S. value.

Referring next to Mr. Field's paper, I wish to point out that from

equation (9) and the further condition K = ^ it clearly does not follow

that the arrangement of branched circuit indicated will be equivalent
to a simple non-inductive resistance of r ohms for all frequencies, since
the equation (9) involves the frequency.

[Note added later. On investigating the matter fully, I find that

balance for all frequencies may be obtained by making K = ^, and

that this is the sole condition required ; Mr. Field's equation (9) is not a
necessary condition. Thus Mr. Field's final result is correct, although
his manner of arriving at it is entirely erroneous.]

I must further tax Mr. Field with using terms which are out of date.
He speaks of ohmic resistance, I should like to ask Mr. Field whether
there is such a thing as a resistance which is not ohmic. Then he
speaks of the secohm. I should like to know what the secobm is. It
is to be regretted that Mr. Field does not see fit to use the modern unit
of self-inductance — the henry. Again, Mr. Field uses the term " self-
induction " in two totally different senses. I should like to suggest the
^se of thp term " leakage self -inductance/' and then nobody can possibly

1903.] AW) FIELD: DISCUSSION. 761

make a mistake ; the matter is perfectly clear. If you define self -indue- P">f- Hay.
tion in one way and then proceed to use it in a totally different sense,
confusion is bound to result.

In Part 2 of the paper Mr. Field states that he is perfectly aware
that the peculiar effects obtained during the charging of a condenser
are treated mathematically in the various text-books on the subject,
impl3ring that the subject had not been dealt with experimentally
before. If Mr. Field is interested in the subject> I can give him
references to several papers in which curves similar to those he gives
are plotted to scale, showing not only the oscillations of the charging
current of the condenser, but also the abnormal rises of potential which
are produced.

[Note added later. The references are : — Phil. Mag, for 1892
(voL xxxiv., p. 389) ; Proc, Roy. Soc. for 1893 (vol. 54, p. 7) ; The
Electrician for 1895 (vol. xxxv., p. 840.]

In connection with the higher harmonics of alternating E.M.F.
waves, it may be interesting to refer to an arrangement — recently
patented by Arnold, Bragstad, and la Cour — in which the property
possessed by the third harmonic in a three-phase system is utilised.
It is not difficult to show that there can be no third harmonic in the
P.D. wave between any two wires of a three-phase system supplied by
a star-connected three-phaser ; for, since a phase-displacement of
i period for the main wave corresponds to a phase-displacement of a
whole period for the third harmonic, the E.M.F.s corresponding to this
harmonic will at every instant be equal and all act either towards
or else away from the neutral point. But if the neutral points of
generator and motor or transformer (star-connected) be connected
through a lamp or motor load, a path will be provided for the
high-frequency current corresponding to the third harmonic.
Such an arrangement, originally proposed by Bedell, would, how-
ever, be practically useless on account of the choking effect of the
motor or transformer circuits. Arnold and his co-workers overcome
the difficulty by distributing the winding corresponding to each
phase over two cores, the connections being such that while for the
low-frequency three-phase currents the action remains unaltered, for
the high-frequency current the motor or transformer coils are non-
inductive. In order to obtain complete control over the high-frequency
single-phase E.M.F., the inventors use a stationary armature, in whose
core are embedded the conductors of the three-phase winding, but the
fly-wheel magnet carries a double set of pole-pieces, one corresponding
to the low-frequency three-phase E.M.F., and the other — thrice as
numerous — ^giving rise to the single-phase E.M.F. of thrice the
frequency. The advantages of low frequency for power work and
of high frequency for lighting are combined in this folycyclic system,
as it is termed by its inventors. A considerable saving of copper is
claimed for it, in addition to its other advantages.

Mr. M. B. Field : In common with the previous speakers I attach Mr. Field,
great importance to the subject of dielectric hysteresis. I think that in
all probability it may be intimately connected with the breakdown
voltage an insulating material will stand. What I mean is this : H one

752 CONSTABLE AND FAWSSETT [Mar. 26th'

Mr. Field. takes a number of similar slabs of a given dielectric and tests them up

to the breakdown point it would probably be found that, other things

being equal, that sample will break down first which has the greatest

dielectric loss, and I would go further, and say that in any individual

sample, provided the electric strain is uniform over the surface, it will

probably break down at that spot where the dielectric loss is a maximum.

If this be correct it gives us a very good reason for examining minutely

this question of dielectric hysteresis quite apart from the cost of the

lost power thereby engendered.

Before touching on that point, however, I would like to call attention

to the fact that the losses to which Messrs. Fawssett and Constable

particularly refer are not wholly confined to the dielectric ; a portion, a

very small portion it's true, occurs in the copper itself, so that a cable on

open circuit which is insulated with a perfect dielectric will always have

a power-factor somewhat greater than zero due to the CR loss in the

copper core which the charging current gives rise to. If C be the

charging current, or that flowing into the near end of the cable, and R

is the total resistance of the ** go and return " conductors, the copper

C*R
loss will be . The apparent power is V C, hence the power-factor

is —

or writing C as 2 tt « K V, /? being the frequency and K the total capacity
in farads, we may say roughly that —

P.F.= 2«KR.

This shows us that the p.f. is proportional to the square of the length of
the cable and to the frequency.

Now with ordinary lengths of cables at ordinary frequencies this
power factor is extremely small, e,g, taking lo miles of No. y cable we
should get —

P.F.= 2 X 6o X 8-36 X 8-8 X 10^ = 0088.

This of course is a very small pi., but if a thirteenth harmonic were
present in the wave-form, the p.f. relative to this one harmonic would
be over •! i or practically as great as that noted for Cable 7 in Table IV.

The above rough approximation can of course not be applied for
very long cables. In that case we should have to express the p.f. in the
following wav :

If V = Vo sin k t
C = CoSin(*/ 4- n)
at the near end of the cable, then 17 may be split up into three compo-
nents, ij = 0 4- e 4- 0,.

The values of ^ and 9 are given in my paper on page 689, while ^,
is such that —

. „ ^ f'""^ sin 2 a /
tan 0,= ,

Now if we assume the resistance of the copper is vanishingly small
^ =5 0 and 0 + 0, = - , which shows us that in this case only can

1903.]

AND FIELD: DISCUSSION.

763

the power factor be zero. Having now disposed of that component of Mr. Fidd.
the loss which occurs in the copper itself, we must look to the dielectric
as the seat of the greater proportion of the total loss.

It is very striking that this dielectric loss can amount to more than
one-third of the total C'R loss in the H.T. cables, for this is what
Messrs. Constable and Fawssett tell us.

Towards the end of the first volume of Maxwell the case of a
stratified dielectric is mathematically considered, in which different
values of conductivity and specific inductive capacity are assumed for
the different layers and the phenomena of electric absorption and
residual discharge are explained on that hypothesis. We then find the
statement that the same reasoning applies and similar results are
obtained if instead of assuming definite strata, we consider merely a
conglomeration of particles with different constants as above. This is
a very useful conception in connection with many manufacturers' insul-
ating materials. Returning to the simpler conception of a stratified
dielectric of which some of the strata act more or less as slightly conduct-
ing layers and take up little of the static strain, while others act more

Fig. F.

A = watts generated per square inch of surface due to given
voltage at given frequency ; B B, Ba = watts dissipated (with
different temperature of surroundings).

truly as the dielectric medium in say an air or mica condenser, we see
that we could consider a section of the insulation of the cable say
between the inner and outer conductors as a succession of capacities
and high resistances in series. Testing such a combination with a con-
tinuous current, it is clear that the insulation resistance might be very
high, since the good layers would take up the static strain. Testing
with an alternating current, however, one might find considerable loss
and heating owing to the capacity currents flowing through the
bad or semi-conducting layers.

In this case the loss would be proportional to the square of the
voltage and to the square of the frequency, while the power-factor
would be proportional to the frequency.

I notice in Table V. the approxinjate Ipss in a paper cable is shown ?

754 CONSTABLE AND FAWSSETT [Mar. 26th,

. Field. proportional to the square of the voltage, and I would like to ask how
this table was derived, whether it rests on experiment or theory.

I said just now that it was probable the " breakdown " strength of an
insulating material was closely related to the dielectric loss, and I
would like to explain what I mean.

If we place a uniform slab of some dielectric compound between two
.netal plates so as to form a condenser, apply an alternating voltage, and
measure the loss per unit area of surface at different temperatures
of the dielectric, we find that after a certain temperature is reached, the
loss increases at a very rapid rate. Now the rate at which the heat can
get away from the slab naturally depends on a large number of circum-
stances, but principally upon the difference of temperature between the
slab itself and the surroundings. Superimposing the two curves of
watts generated (due to a given alternating voltage at given frequency)
and watts which can be dissipated (by conduction, radiation, etc) per
square cm. of surface, we get curves such as A and B in the figure
above. At the temperature /, the heat generated is greater than that
got rid of, so the temperature of the material would tend to rise. At
the temperature 4» on the other hand, the energy which the slab can get
rid of per second is greater than that generated, hence there will be a
tendency for the material to fall. T will therefore be a temperature
at which the material will eventually arrive, since at this temperature
the rate of generation of heat is equal to the rate of dissipation.
Should however the temperature of the slab by any means rise above
T„ it might be said to be in an unstable state, for the temperature would
then continually increase until the insulating properties of the material
were destroyed by charring. The effect of increasing the temperature
of the surroundings will be to materially raise the final temperature T
to which the material will rise, for in this case the curve representing
watts dissipated will be B, instead of B. Again, if we increase the
surrounding temperature still further, we find that there will be no final
temperature at all, but that the slab will get hotter and hotter until it
chars. If now there is a spot in the slab which is weaker than else-
where, more heat per unit area will be generated here, and the temper-
ature will rise locally at this point. In fact, it seems possible for the
temperature to rise at a weak spot to such a limit that actual scorching
occurs there without the rest of the material being damaged. As soon
as this occurs the insulation breaks down, an arc follows, and in all
probability destroys all traces of the gradual burning which has pre-
ceded. In corroboration of this theory, which was verbally explained
to me by Mr. Miles Walker after he had conducted a number of experi-
ments in this direction, I would instance the following facts.

ist. The voltage that many materials, such as paper, prepared linen,
prcsspahn, etc, will stand depends in some way inversely as the time
of application. For example, a layer of paper will often withstand
15,000 volts for an instant, when it will not stand 5,000 continuously.

2nd. If slabs be tested as above described, and the voltage be applied
for gradually increasing periods of time, and if they are examined after
each application, it will often be found that scorching has occurred at
some point without actually brea ing down, and if the material be

1903.] AND FIELD: DISCUSSION. 755

again tested under electric pressure it will finally break down at this Mr. Field,
point.

3rd. In testing insulating tubes, etc., it is quite a usual practice to
put a number under a high voltage test for a few minutes and then to
feel them. The hot ones are cast aside as bad, since it has been found
by experience that these would in the long run give out.

4th. Those materials which do not change their composition when
subjected to a high temperature are usually found to be the best insula-
lators, e.g., mica, porcelain, glass, ambroin, and even air. Should the
above theory be correct, we see that it will lead us to the important
conclusion that the breakdown strength depends also on the frequency,
and a material which easily burns would be much stronger if tested
with continuous voltage than with an alternating. We further see that
inflammable materials will have two strengths entirely different, one in
withstanding mechanical piercing due to a strain of very short duration
where the heating effect cannot come into play, and the other in with-
standing prolonged strains. It seems probable that air and certain
other insulators only break down through piercing, i.e., in the first-men-
tioned manner.

To my mind a careful investigation into this whole matter would be
of the greatest practical importance to the designers of electrical
machinery.

Mr. W. M. MoRDEY : Mr. Constable and Mr. Fawssett deal with the Mr.
distribution losses in the very practical form of a detailed examination Mordey.
of the actual losses in the Croydon system. Although we have at this
Institution often discussed the subject of lost units, I do not think it has
ever been put before us in so telling and complete a way. It is saddening
to think that after all the efforts of the last twenty years the losses in a
well-considered distribution system should be 22 per cent, of the energy
sent out of the generating station.

Such a paper shows clearly the direction in which we must work if
we desire to reduce the distribution losses. Some of the losses can
only be reduced by an outlay which would be unsound commercially,
but some may perhaps be lessened.

The authors treat only of distribution losses. When they have
exhausted that subject they may turn their attention to the inside of
the station, when they will find there is a loss of coal of about 50 per cent,
which, on paper at any rate, is capable of being saved. Then they may
study the loss of about 85 per cent, in converting the heat energy of the
coal into mechanical energy in the boiler and engine ; and when they
have studied those few small losses they may continue their investiga-
tions and consider the loss of more than 99 per cent, in the incandescent
lamp itself between the heat energy given to the lamp and the light
energy given out.

You will find, sir, that we shall not exhaust this subject to-night !

Before going on to the matter that interests me a good deal, that of
the losses in the dielectric, I would like to refer to the question of
switching transformers off, mentioned by the authors at page 723.
It is generally believed that for economical working it is necessary
to keep transformers as nearly fully loaded as possible — this is

756 CONSTABLE AND FAWSSETT [Mar. 26th,

Mr. not by any means the case. There is often no advantage in

*^* switching transformers off; there may even be a disadvantage in
doing so. The efficiency curve of a good transformer is square-
shouldered ; it goes up quickly, to practically full efficiency, and then
keeps nearly straight up to full load, often indeed falling a little as full
load approaches. Now with such conditions two half-loaded trans-
formers are as efficient as one fully loaded ; if the curve drops a little,
the two will be even more efficient.

For transformers having efficiency curves which reach practically
full value at one-third load, three of them, each one-third loaded, will
be as efficient as one fully loaded. Under such conditions it is best not
to keep transformers fully loaded ; it does not save energy, and it is
bad for the transformers. If a given amount of energy is to be wasted,
it is better to spread it over a number of transformers than to concen-
trate it in one — better for the transformers, and it lowers the copper loss.

Turning now to the question of losses in the dielectric of the cable,
I quite agree with the authors in disliking the term. If the last speaker
— who seems to have a liking for correctness in terms — could invent
some term which is less cumbrous and more like Anglo-Saxon than
"dielectric hysteresis," we should all be very grateful to him.

The paper that I read here some time ago on that subject has been
referred to by the authors and by one or two speakers. I was rather
badly treated in that discussion ; it was apparently felt that in sug-
gesting we had overlooked a serious cause of loss of energy, I had
committed a crime of the most heinous character ! But time brings
its revenges. As the authors say, the subject was not exhausted then,
and I am very glad indeed they have contributed to its further elucida-
tion. There is a good deal to be done before we have got to the bottom
of that subject. But it is one that we must consider. If there is a
possibility of power-factors of anything like the order I mentioned in
my paper — now confirmed by the present authors— or, I will go further
and say that if there are power-factors of a much lower order — such as
Mr. Duddell says he is satisfied do commonly exist — it is a matter of
real engineering importance, especially for long distance high-pressure
work. We must try and find some simple way of measuring these
losses. The authors and Mr. Duddell — ^an investigator who should be
carefully cherished — have used certain methods which are probably
the best now available, but we want something more direct. I would
suggest calorimetric methods. Direct measurement of the rise of tem-
perature is of course hardly practicable. Under ordinary conditions
even a serious loss of energy would not cause any noticeable rise of
temperature in a cable.

It ought, however, to be possible to put a cable into a heat-
insulated bath of oil or water and to run it and observe the rise
of temperature that takes place when it is subject to high electro-
motive forces. It should then be possible to get the same rise
and therefore the same loss by sending a direct current through
the conductor of the cable and so measure the direct current energy
easily. I do not say there are no difficulties. To what extent the
losses are eddy-current losses is a matter to which attention must

1903.] AND FIELD: DISCUSSION. 757

be given. But I think there are ways of making calorimetric test.s Mr.

under conditions where, if eddy-current losses exist, they may be kfept
so small as to be negligible, or, in any case, their amount can be
measured. This latter might be done by determining the loss, other than
that due to resistance and current, by sending a low-tension alternate
current through a cable in the calorimeter; under these conditions
there would be no dielectric loss.

When I read a paper on Capacity Effects before this Institution, the
discussion was associated with a good deal of heat other than what is
usually measured by a thermometer. I hope we shall now discuss it
calmly and find out seriously whether it is a loss which engineers-
makers or users of cables — need consider. It is far more important to
be sure that there is a small dielectric loss than that the copper has a
high conductivity. If it is necessary to specify the latter carefully,
much more important is it to consider a cause of loss which may be
hundreds of times gre^lter than that caused by the copper being 0*96
instead of 0*98 of Matthiessen's standard of conductivity.

May I be allowed to give as an example a few figures to show that
this matter is of real importance even with small power-factors ? It is
not denied, I think, that there may be such power-factors as o'l, but let
us take the lower values of 0*025 or 0*03 which Mr. Duddell's experi-
ments lead him to say need not be exceeded in any good cable. I do
not, however, agree with him that with such values the matter is of no
importance ; even a o'oi power-factor may be of importance. Let us
take a case which may easily occur in practice. Assume a 10,000-volt
three-phase cable for a transmission system supplying such an area as
many power schemes are now proposing to deal with. Assume it has a
capacity of 0*3 microfarad per mile, and a power-factor of 0*03 — then
the loss would be 7,400 units a year for every mile of cable, or about
equal to an 8-c.p. lamp, always alight, for every 63 yards of cable.
Assume this cable is ten miles long and is supplying a small town
having an ordinary 12 per cent, load-factor and a ** maximum demand "
of 300 kw. — the ordinary " authorised distributor " of the power bills —
then the dielectric loss in the cable will be 23*4 per cent, of the energy
delivered, or as much (in percentage) as the authors show is lost in the
whole system at Croydon in transmission and distribution.
If this is true, the question deserves serious attention.
It would be interesting — in these days of power bills and long-
distance high-pressure schemes — to follow this point a little further,
but I will only point out that if the copper loss in this cable is 5 per
cent, and if the ** authorised distributor " loses only 20 per cent, in
distribution, then the generating station must send into that cable about
48*5 per cent, more energy than ever reaches the customers. One point,
however, must not be lost sight of : the dielectric loss, whatever it may
be, does not greatly increase with the size of the cable ; thus it will be
relatively less serious on a cable for a large load than for a small one.
For the latter it may be serious enough to prevent the economical
supply of small towns through long underground cables, and may
strongly support the demand for bare overhead conductors.

One other point— this loss is not a capacity loss at all, but a kind of

MorJey.

758

ELECTIONS.

[Mar. 26th,

Mr.

Mordcy.

resistance loss having a unity power-factor of its own ; it would take
place just the same if the cable had no evident capacity.

The President announced that the scrutineers reported the follow-
ing candidates to have been duly elected : —

Ovide F. Domon.

Members,

I Giovanni Giorgi.
Wyndham Monson Madden.

Associate Members.

Frank Anslow.
Robert Malcolm Campbell.
Johan Denis Carlmark.
John Mathieson Kcenan.

Walter Henry Le Grand.
John F. Magoris.
John Frederick Pierce.
Theodore Rich.

Harold Stokes.

Associates,

Arthur Chester.
Edward Alan Christian.
Wm. Frederick Coakcr .
Wm. Thomas Dalton.
Theodore J. Valentine Feilden.
Thos. Henry Flam well.

John Walker Fyfe.
Chas. Ward Hammertoa
Hugh Henry McLeod.
Chas. Edward Harrison Perkins.
Louis Boniface Wilmot.
Clifford George Woodley.

Students,

Herbet Paul Amphlett.
William Bell Begg.
Eric Frank Cliff.
William Prescott Crooke.
Thomas Davies.
Henry T. Debcnham.
Eustace Jonathan Down.
Henry Firth.

Martin Julius Wolff.

Charles Butter Grace.
Harry LilPwhite.
Joseph F. Mongiardino.
Leonard John Pumphrey.
Chas. Alexander Rainsford.
Roy Grosvenor Thomas.
Geo. Keenlyside Tweedy.
James L. Wilson.

1903.] TRANSFERS, DONATIONS TO LIBRARY, ETC. 769

The Three Hundred and Ninety-second Ordinary General
Meeting of the Institution was held at the Institution
of Civil Engineers, Great George Street, Westminster,
on Thursday evening, April 23, 1903 — Mr. Robert K.
Gray, President, in the Chair.

The minutes of the Ordinary General Meeting held on March 26th,
1903, were taken as read and signed by the President.

The names of candidates for election into the Institution were
taken as read, and ordered to be suspended in the usual form.

The following list of transfers was published as having been approved
by the Council —

From the class of Associates to that of Members—

Walter Joseph Higley.

From the class of Foreign Members to that of Members^ —

Frederico Pescetto.

From the class of Associates to that of Associate Members —

Frederic Robert Bridger. I William Richard Kelsey.

Robert Marshall Carr. I Theodore Arnold Locke.

Robert Tyndall Haws. j Arnold Philip.

Francis C. Hounsfield. | Maurice Solomon.

T. B. Wright.

From the class of Students to that of Associate Members —
Frederic Chas. Kidman. | John Warrack.

From the class of Student to that of Associate —
Arthur John Cridge. | Alfred Eddington.

Messrs. H. Brazil and L. T. Healey were appointed scrutineers of
the ballot for the election of new members.

Donations to the Library were announced as having been received
since the last meeting from Messrs. A. Hcyland, H. A. Humphrey,
E. and F. N. Spon ; to the Building Fund from Messrs. B. G. Jones,
H. T. Lines, A. Nield ; and to the Benevolent Fund by Mr. S. E. Britton,
to whom the thanks of the meeting were duly accorded.
Vol. 82. 60

760

MEMBERS NOMINATED BY THE COUNCIL [April 28rd,

The Secretary read the following nominations by the Council for the
officers and Council for the ensuing Session ; —

MEMBERS NOMINATED BY THE COUNCIL FOR OFFICE

1903-1904.

Nomination,

Remaining in Office,
New Nominations,

As President,
Robert Kaye Gray.

As Vice-Presidents (4).

(John Gavey.
(Sir Oliver Lodge, F.R.S.
( Dr. J. A. Fleming, F.R.S.
Ij. E. Kingsbury.

Remaining in Office,

New Nominations,

Ordinary Members of Council (15).

/Sir John Wolfe Barry, K.C.B., F.R.S.

S. DOBSON.

Bernard Drake.
H. E. Harrison.

1Lt.-Col. H. C. L. Holden, R.A., F.R.S.
The Hon. C. A. Parsons, F.R.S.
W. H. Patchell.
J. H. Rider.
A. A. Campbell Swinton.
/T. O. Callendar.
S. Z. DE Ferranti.
Frank Gill.

F. E. Gripper.

G. Marconi.
W. M. Mordey.

As Associate Members of Council (3).

Remaining in Office,
New Nomination,

For Re-Election,

For Re-Election.

(W. DUDDELL.

(Sydney Morse.
A. J. Walter.

As Honorary Auditors,

( F. C. Danvers.
(Sidney Sharp.

As Honorary Treasurer,
Robert Hammond.

As Honorary Solicitors,
Messrs. Wilson, Bristows & Carpmael*

1903.] FOR OFFICE 1903-1904. 761

The President : Before the discussion of the papers of Mr. Field
and Messrs. Constable and Fawssett is op^ened, I desire to ma^e a few
remarks with regard to the recent visit to the North of Italy of about
I20 members of the Institution. The object of these remarks is to
place on record, in the Proceedings of the first meeting held "since our
return, the sense of gratitude felt by the Institution for the great
kindness shown by our Italian hosts.

In addition to the many interesting visits which had been arranged,
the very cordial reception given to the party was quite remarkable.
Senator Colombo, who had been in Rome, made a point of coming to
Milan to meet us. Professor Ascoli, the President of the Associazione
Elettrotecnica Italiana, also came from Rome to preside at the banquet
given in our honour by that body. Mr. Blathy, of Messrs. Ganz and
Co., came specially from Buda-Pest to assist in showing us the Valtellina
line, in the electrification of which his firm played a preponderant role,
Mr. Cini, of the Adriatic Railway Company, who are interested in the
Valtellina line, came from Florence. Our visit to the Tornavento Power
Station, with the inspection of the electrified Milan- Varese line, was
rendered more instructive and agreeable by the presence of Mr. Kossuth,
one of the Directors of the Mediterranean Railway Company, and of
Monsieur Lagout, of the Thomson- Houston Company de la Mediter-
ranee, who came from Paris with the object of accompanying us and
showing us the work of his firm. Senator Colombo and his friends
showed us the large water-power station, at Paderno, of the Italian
Edison Company, and also their Distributing Stations in Milan. Senator
De-Angeli conducted us to the Vizzola Water-Power Station of the
Societa Lombarda per Distribuzione di Energia Elettrica. In addition
to these, the Chairman of the Milan section of the Associazione Italiana
Elettrotecnica, Mr. Bertini, and the Secretary — Mr. Semenza — had,
through the courtesy of the proprietors, enabled us to visit several
works in the neighbourhood of Milan and in Milan itself which proved
of great interest to the visitors. It is impossible to thank Mr. Semenza
too much for the enormous labour he must have gone through to
provide for the entertainment of a numerous body. The Council will in
due course tender the thanks of the Institution to our late hosts in a
more formal manner.

Before terminating I think I should inform the members of the
Institution that the visit to the North of Italy is considered by all who
took part in it as a very successful one, and that Dr. Silvanus Thompson,
who had taken so much trouble in initiating it, Mr. Hammond, the
reporter of the Foreign Visits Committee, and our Secretary — Mr.
McMillan — who so successfully carried out all the details of the expedi-
tion, certainly earned the praise which they received from all sides.

With these remarks I shall now call upon Professor Carus- Wilson to
open the adjourned discussion on the papers read by Mr. Field and
by Messrs. Constable and Fawssett.

762 CONSTABLE AND PAWSSETT [April 23ni,

Resumed Discussion on Papers on ** Distribution Laws in Elec-
Tinc Supply S\'stems," by A. D. Constable, A.M.LE.E., and E.
Fawssett, A.LE.E., and "A Study of the Phenomenon of
Resonance in Electric Circuits by the aid of Oscillograms,"
BY M. B. Field, M.LE.E., A.M.LC.E.

Pro^ Caru8- Professor C. A. Carus- Wilson : Mr. Field has brought before us a
subject of great importance and interest, and has illustrated his paper
by showing us some interesting slides. Mr. Duddell has supplemented
what Mr. Field has given us by further illustrations of resonance in
transmission circuits, and the jagged, saw-like curves which he showed
were calculated to alarm us, especially when accompanied by statements
that they involved very high voltage. The question I want to raise
to-night is whether the effects that have been shown to us are really
serious, in view of the actual strains to which high-tension circuits are
subject in every-day working. Mr. Field in his paper rightly alludes to
what has been written on this subject in the United States, and draws
attention to the communications that from time to time have appeared
on this subject in the transactions of the American Institute of Elec-
trical Engineers. I quite agree with him in thinking that those transac-
tions are not as well read on this side as they should be, and I am also
surprised that more members of our own Institution are not members
of the American Institution. I notice, however, that his paper gives
us several results which have already been arrived at by other workers.
For instance, the equations he gives us at the bottom of p. 685, for the
induced pressure due to sudden and rapid oscillating effects consequent
upon breaking a circuit with a load on, are the same as those given by
Mr. Steinmetz two years ago, though arrived at by a different process.
On p. 691 the equations that Mr. Field gets for the rise of pressure, due
to resonance, at the end of the long transmission line, appear to me to be
identical in result, with some slight exceptions, to which I will refer
later, with those given by Houston and Kennelly in 1895. I refer to
these facts simply to point out that Mr. Field has arrived at the same
results by working out these problems on independent lines from his own
standpoint, in a way quite different from what others have done. On
p. 691 Mr. Field gives the fundamental conditions for resonance, and an
equation for the rise of voltage at the end of a long transmission Une.
I do not see why he needs such a confusion of terms at the bottom of
p. 688, where he introduces Greek letters as well as Roman letters ; 1
have not quite been able to follow him in that. Surely it is simpler to
express the condition of maximum resonance by the expression —

In the way Mr. Field gives it we have to look back to a complicated
series of equations in order to understand it. [Communicated, After
hearing Mr. Field's explanation of his symbols I admit that his equa-
tions are quite as simple as the one I have given above.] I should like
to show on the blackboard what this distance / really is. If A is the
receiving end and H the sending end, then the pressure is a maximum

1903.]

AND FIELD: DISCUSSION.

763

of V, volts at A, and as we get nearer the sending end the pressure
drops to a minimum of Vo volts, and rises again if the line is long
enough. The length / between the positions of maximum and minimum
pressure is given by the above equation. In practice this distance is very

Prof. Canis-
Wilson.

Fig. G.

great. In a case which I had occasion to work out recently for a three-
phase transmission line about loo miles in length, this distance came
out to 1,430 miles, that is to say, in order to get the maximum resonance
effect the line would have to be 1,430 miles long, whereas the line was
only 100 miles long. Consequently the actual rise of voltage due to
resonance was a mere nothing. In the next equation Mr. Field gives us
an expression for the relation between Vo and V„ from which we can
find the rise of pressure due to resonance. I cannot help thinking that
Mr. Field or his printer has made a slip in that equation ; he has in the
denominator —

I think that should be —

— 2 t'~ * ^''*" *^

-f- 2 t'~ ftantf

for then that rather complicated equation becomes simply —
V«

= cosh / a

That is the usual form of the expression for this ratio, where / is the
length in miles and a is the quantity depending on r, \, and ;}.

In the case of the long transmission line to which I referred, taking
L at 100 miles, the total rise in voltage did not amount to more than
2 per cent., that is to say, not only is the line required to get the maxi-
mum resonance effect of great length, far beyond anything that we get
in practice, but the actual rise is quite insignificant. I think it is now
generally recognised that resonance effects in long distance trans-
missions are really of no importance. When we get the frequencies of
the higher harmonics that Mr. Field's paper deals with, we get r^son-

764 CONSTABLE AND FAWSSETT [April 23rd,

Prof. can». ance effects, but they are so small, on account of the very small ampli-
tude of the waves that are magnified, that the increase in pressure above
the normal voltage is a very small percentage when you compare peak
with peak or mean with mean. I take it, then, that in actual practice
these resonant effects are extremely small in long-distance transmissions,
even when you take account of the higher harmonics. But not only
that, the effects of resonance, to which allusion has been made by Mr.
Field and Mr. Duddell, are altogether insignificant when you come to
consider the strains that are actually put upon high-tension transmission
apparatus by oscillating discharges. I notice that Mr. Field refers to
all the effects dealt with in his paper as resonance effects. I have
always understood that the term resonance referred to a stationary wave,
the kind of thing shown in the diagram, which is a permanent condition
of affairs. That was the meaning of the term adopted by the people
who introduced the expression ; but in this paper, and in other places
also, resonance has come to be applied to a great many other effects
accompanying high tension ; for instance, oscillatory effects. I quite
think that those are the phenomena we have to fear in a transmission
circuit, but they are not resonance effects at all, since they are not due
to stationary waves — they are due entirely to momentary changes in the
conditions of loading the line. These arc the really important effects to
be considered, since they subject transmission lines to enormous ten-
sions, far greater than any due to resonance. It would be a good thing
if we could get some more tests made on these oscillatory effects. The
equation for V on page 685 of Mr. Field's paper gives the pressure
caused by suddenly breaking a circuit with a load on. The term

f V,* -f- C 1^ J indicates the degree of strain that is put upon the

insulating material, from which it appears that the strain upon the insula-
ting apparatus depends upon the load, and is proportional to the current
that is being broken, and that if the circuit could be broken when
C =: O there would be no rise of pressure. This is entirely borne out by
tests made on some long-distance transmission lines in the United States,
when it was found that the high voltage induced by breaking the circuit
was entirely a question of the load that happened to be on the circuit at
the instant of the break. When the load was broken under oil, the
effect of the break, as shown by means of an oscillograph, was like this : —
There is an oscillating discharge extending for a
few waves, and then the oil breaks the circuit at
the zero point. 'If it were not for the fact that
an oil switch breaks the circuit at zero point, I
think it would not be too much to say that high-
tension long-distance transmissions carrying very
large currents would be impossible. But it is
Fig. H. found in practice that the effect of oil is to allow

the arc to spring just for a short time, extending
over about half a dozen waves, and then to break the circuit at the
zero point, that is to say, in a remarkable way the oil switch does
exactly what we should want it to do, and breaks the circuit at the
moment when the current is nothing, thereby enabling the circuit to be

1908.] AND FIELD: DISCUSSION. 766

broken without any rise of pressure. In the tests I referred to, currents Prof, carus-
of 30 amperes at 40,000 volts were broken by an oil switch without any *°°*
rise in the voltage being shown on the oscillograph. The danger of
breaking a high-tension circuit may thus be less than that of making
the circuit, for I do not know of any switch by which the high voltage
that you get when making a transmission circuit can be prevented,
unless, of course, rheostats are used. It would appear, then, that
transmission circuits may be subject in ordinary working to very high
pressures due to oscillatory discharges altogether out of proportion to
the effects due to resonance, twice, or even three times, that of the
normal voltage. I therefore endorse what Mr. Field says at the end of
his paper that the oscillatory effects are those that need most to be
studied by means of the apparatus we have at hand, notably the oscil-
lograph.

{Communicated) : In criticising Mr. Field's equation on page 6qi, I
was under the impression that he was using the terms involving the
resistance, self-induction, and capacity as vector quantities, in which
case the expression for the ratio of the squares of the pressures at the
two ends of a transmission line on open circuit is of the form

i(cosh2R/ 4- i),

R being a constant involving the capacity, etc., and / the length of the
line. I see now, however, that he is not using vectors but numerical
quantities, in which case the expression is of the form

i (cosh 2 P / 4- cos 2 Q /).
Q/ is the angle of advance in phase of the pressure as the sending end
is approached ; for maximum resonance this angle is - , so that this
expression then becomes

i(cosh 2P/— i),

and this is the equation given by Mr. Field, putting cosh for the more
complicated exponential terms used in his paper, the sign being rightly
negative.

Mr. G. L. Addenbrooke : My remarks will bear upon rather a Mr. Adden-
different part of the subject to that alluded to by the last speakers.
The paper covers so much ground that it is impossible to deal with all
the points in it. As I have had considerable experience in testing
cables for what is called dielectric hysteresis, perhaps some account of
what I have done might be interesting. My own work began in the
following way. Dr. Muirhead some two years ago lent me some of his
special condensers for the purpose of investigating the losses which took
place in them. I had been too busy to do anything with them up to the
date of Mr. Morde/s Institution paper two years ago, but startled by
his results I forthwith began some tentative experiments which I men-
tioned in the debate. Shortly after, I received a communication from
the Henley Telegraph Cable Co., who were concerned from a com-
mercial standpoint, and who were rather upset by the possibility of this

brooke.

766 CONSTABLE AND FAWSSETT [April 2Srd,

Mr. Adden- large dielectric hysteresis loss. The result was that they asked me to make
some investigations at their works on the subject. The first question
which arose was, how these experiments should be made. That really,
I think, is the matter which is before us at the present moment, because
it is not much good having experiments made until we are pretty certain
that the means used for making the experiments are likely to give fairly
correct results. I therefore went into this matter. My idea was to
employ the electrostatic system of measurement, which I described
generally at the International Congress at Paris two and a half years ago.
When I came to look into it, it seemed that it would be suitable, and
also that it was adapted to meet the following very important point.
Going into the calculations with regard to air core transformers for
insertion in the circuit, I found it usually meant that you must have
three or four tnicrofarads capacity in the cable, in order to keep
your air core transformer within reasonable limits, which of course
means a long length of cable, which it is very troublesome to deal
with and is not very commercial. By using the electrostatic system,
even as the system stood intended for ordinary work, I found one
could go down to half microfarad with, it appeared to me, a fair
chance of being pretty accurate. There is no doubt that by special
arrangements it is possible to measure electrostatically the loss in very
smaU capacities indeed— in fact, since the date of my experiments, in a
paper in the journal of the American Institute of Electrical Engineers f}AT,
Miles Walker described how, by means of a special electrometer used
in order that the high pressure might be directly applied to it, he has
been able to make dielectric hysteresis measurements on slabs a foot or
two square. Therefore it is clear that, apart from its suitability other-
wise, the electrostatic system has very great advantages for the com-
mercial measurement of dielectric hysteresis, because we can deal with
very moderate lengths of cable.

My apparatus being set up at Messrs. Henley's, arrangements were
made for carrying out tests from 2,000 up to about 6,000 volts, and I will
give you a few specimens of them. About '9 of a microfarad of un-
armoured lead-covered concentric cable was tested between the inner
and outer. I may say that the arrangements at Messrs. Henle3r's did
not, unfortunately, permit of a constant periodicity in all tests being
obtained, because they had to vary the speed of the alternator to some
extent to get the different voltages, so that the experiments are not so
comparable directly as they might have been, but when allowance is
made for this they all come very close to each other. The results I
got are given in Table I. It is to be noted that the power-factor
gradually rose as the voltage rose. Another point that turned up in these
experiments was that the results are all somewhat lower than those
published by Mr. Mather, which were also conducted on paper cables,
and which he mentioned in dealing with Mr. Mordey's paper. Of course
there may be different sorts of paper, but as most cable makers deal
with the same class of paper, I did not think the difference could
altogether be accounted for that way. The question therefore arose
whether the difference was due to differences of measurement or to the
material. Of course, also, there might have been possible differences

19(».]

AND FIELD : DISCUSSION.

767

due to the wave forms that were used in the experiments. Unfortu-
nately, as regards this, I had not the means at my command at the time
of ascertaining what these forms were, but I doubt if this can account
for all the difference. However, while I was still considering this
question some measurements had to be made at Wood Lane on a large
inductive resistance which I designed for Messrs. Willans and Robinson
for enabling alternators to be tested at proper power factors and which
was specified to carry a certain current for six hours at 5,000 volts without
undue heating. From the ordinary calculations on a resistance of this

Mr. Adden-
brookc.

TABLE I.

Cable Tests at W. T. Henley's Telegraph Works, Ltd.

Capacity '9 mf. Unarmoured lead-covered C.C. Test between Outer

and Inner,

Volts.

Amperes.

Watts.

Periods.
287

Power Factor.

Actual.

Calculated.
•33

Per cent.

2,040

•24

5-1

1*04

2,000

•388

•536

IO-4

1-34

3,000

•36 • -486

167

3,000

•55 7

I '46

4,000

•36 -452

267

1-86

4.040

715 ! -965

1-63

1 5700

•6 1 755

60-4

172

TABLE II.

Cable Tests at Wood Lane.

Capacity. Unarmoured 3 Core. Tests between Cores A, B, C.

Vdts.

5,000
2,500
2,500
5,050

Amperes.

Actual.

Calculated.

Ill

•863

•637

•432

•95

•69

1-68

1-38

Watts.
50

i8-5

32-5
102

50
50
50
50

Power Factor,
per cent

Cores used.
•9

I'lO

1*37

768 CONSTABLE AND KAWSSETT [April 23rd,

Mr. Adden- sort, made for me by Mr. Berry of the British Electric Transformer
*^ ^' Company, we came to the conclusion that the power factor, including
the losses in the iron, ought to be about 4 per cent., and the instruments
correctly indicated about 4 per cent. Therefore I think this is one
fairly strong reason for sajring that the instruments were capable of
measuring power factors of this sort with close accuracy. In the case
of Mr. Miller's cable, which is a three-phase cable, it was tested at 5,000
volts and 2,500 volts. When tested between one core and the other the
hysteresis loss came out at about 1*2 per cent., and in one case as high
as 1*37 per cent. Again, as in Table II., the results are comparable
with the other results I obtained. This was a British Insulated Wire
Compan/s cable of the same kind that Mr. Mather was experimenting
with. Having arrived at this point, I thought I would check my work-
ing by testing with an air core transformer, that is to say, using the
electrostatic system and putting an air core transformer in. For that
purpose Mr. Savage, of Henley's, was good enough to have one con-
structed of flexible, of which they are makers. Dr. Fleming, in his book
on electric testing, has put forward an air core transformer as an excel-
lent means, which it undoubtedly is, of finding out whether a wattmeter
indicates properly on low power factors because you can with it get a
power factor as low as 3 per cent. Having this air core transformer, it
occurred to me that I would test my own wattmeter with it. This I
accordingly did at Messrs. Henley's before applying it to the cable.
The result was that when I came to work out the experiment it appeared
as if there was some loss in the air core transformer itself. In the
debate on Mr. Mordey's paper it was taken as an axiom that there was
no loss in the air core transformer. Not being certain about this, I got
the air core transformer sent up to my own laboratory in Victoria Street,
where I had the Deptford current. It was again tested at about double
the periodicity at which it was tested at Messrs. Henley's. The result
was that the loss went up somewhere about as the square, which it
would do if that loss was due to eddy currents. I may say that in this
case the loss was of the following character. The whole weight of the
copper in the air core transformer was somewhere about one hundred-
weight, and the loss I got at 89 periods was about 36 watts, uc, about
one-third of a watt per pound. When you come to consider the very
large number of ampere turns there are on such a transformer, and
what a very strong field there is, it does not seem impossible that
there should be a loss of this sort. In my case, too, the flexible
wire, which was of the ordinary character, happened to be very new.
In Mr. Mather's case he used an air core transformer of solid No. 14
copper, as far as I understand. I see from calculations that during his
tests he must have had 12,000 ampere turns on the coil, which makes a
very strong field. It seems quite possible that he may have lost 50
or 60 or even more watts in 80 lbs. of copper, which deducted would
make his results nearly the same as mine. I do not wish to cavil
at Mr. Mather's figures. I think he did his experiments somewhat
hurriedly, and that to have got as near as he did in the time was almost
a feat, because it is a very difficult thing to get reliable experiments
with this dielectric hysteresis work. Perhaps I may be allowed to put

1903.] AND FIELD: DISCUSSION. 769

my results into ordinary figures, because I think it is very important we MrAdden-

should recognise that, at any rate for practical purposes, the dielectric

hysteresis loss in itself is not very serious. In the case of Mr. Miller's

cable, which was a three-phase feeder, 2^ miles long, working at 5,000

volts, the actual loss was about 100 watts, or 40 watts per mile. I may

say that that was tested without any load on, and therefore perhaps we

had rather a bad curve, in fact, the main was actually tested afterwards

by Mr. Duddell with the oscillograph, and the results were shown on

the screen at the last meeting. Unfortunately I cannot say now which

of Mr. Miller's cables the test was made on, but it may be of interest to

know that one of Mr. Duddell's results is the wave with which my tests

were made.

There are one or two general conclusions I should like to mention.
On another occasion a fresh set of cables were put up for experiment.
Unfortunately I was not there myself, but my assistant, Mr. Robinson,
who really works my instruments better than I do myself, conducted
them. In this case there was an iron sheath outside the cable, and the
whole of the results came out higher than in other cases. As far as I
know the cables were exactly the same ; this bears out some results that
have been given in the paper we are discussing. I was rather afraid to
publish these particular results at the time, as my theoretical friend
polled a long face, but as the matter has been brought forward in an-
other form, I mention that in that particular set of experiments we did
get 30 or 40 per cent, increase in the loss when the cable was covered
with an iron sheath. There is afnother general point which I think is
worth bringing forward with regard to this dielectric hysteresis loss.
These losses go up with the voltage to some extent ; as a matter of fact
the voltage on one occasion was carried out nearly as high as 11,000
volts, or as much as the cable would stand, with a view of seeing what
would happen. The watt losses go up more than proportionally, so that
if you keep the wattmeter on and watch it, it really forms a sort of
guide to what is going on in the cable, and when you get near the
breaking point you get a very great increase of the watt losses. I am
inclined to think that a measurement of this class may be very useful in
testing cables as to what they are likely to stand, in lieu of simply putting
on a breakdown voltage, or say two or three times the working voltage.
In testing a boiler, no one would think of testing it up to its breaking
pressure, as to do this would cause permanent damage ; and, in the
same way, by putting too high a pressure on a cable its resisting powers
may be permanently injured, but tests, at a few gradually increasing
voltages, of the watt loss with an alternating current will enable
a curve to be constructed from which the behaviour of the cable can
be seen and the point beyond which it is undesirable to press the
voltage can be predicted.

Mr. C. P. Sparks : The two papers before us show how much we Mr. Sparks,
are indebted to Mr. Duddell for the oscillograph. I regret to have to
say this, after so many other speakers have mentioned the matter, but
as I have worked with him a good deal, I feel how much we are
indebted to him for such an efficient instrument to attack some of the
more obscure problems in connection with transmission work. Mr.

770 CONSTABLE AND FAWSSETT [April 23rcl

Mr. Sparks. Field's paper brings prominently before us the diflFerence between the
modern three-phase generators with an irregular wave form, and the
old type of singleiphase machines. In Mr. Field's paper, the author
directs attention to the advisability of localising the characteristics
of each system with the oscillograph. I cordially endorse his recom-
mendation. Some three years ago, my attention was directed to the
effect of running up an excited generator on mains of high capacity
when it was found that as the frequency rose the current passing into
the mains rose suddenly to a high value, and then fell with increasing
pressure and frequency. This occurred twice before the working fre-
quency and pressure were reached. The oscillograph at once showed
what was happening. Some tests which Mr. Duddell carried out for me
with the oscillograph, with the moving film, showed that all variations
in the number of mains, generators, and, in our case, throw-up trans-
formers should be made at standard frequency. Hence it is usually
dangerous to energise a main by running up from a separate generator
or motor-generator, unless the working frequency be reached before
the alternator is excited. At the Deptford station, Mr. Partridge intro-
duced ten years ago the method of energising the mains through a
transformer, the secondary of which was gradually short circuited.
Tests showed this method to be safe, so long as the resistance of the
secondary did not fall below a critical value. The use of such an
apparatus is generally limited to generators of the copper armature
type, owing to the absence of harmonics, and this system cannot
generally be applied to the present form of three-phase generators.
The safest method to switch on a main is through a non-inductive water
resistance, which is gradually cut out over a period of a quarter of a
minute. Last year Mr. Duddell took records of switching on cables
under these conditions, and it was found that as long as a period of
something like a quarter of a minute was taken no undue rise of
pressure occurred in switching on cables, the longest length being 14^
miles. The actual length tested was something like 8 miles.

The modern oil break switch efficiently disconnects the feeders
under normal conditions of load. Mr. Duddell took records which
showed that, as pointed out by a previous speaker, the current is
apparently always broken at the zero point, and under all normal con-
ditions the circuit was broken without any dangerous rise of pressure.
The most dangerous operation is the removing of a short-circuited
feeder, as in addition to the heavy current to be broken the frequency
of the station may be affected. Up to now the only really safe con-
dition to remove such a feeder is by keeping your frequency up,
and reducing the pressure momentarily in order to disconnect the
feeder.
Mr. Mr. A. Campbell : With regard to Mr. Field's method of testing

CampbciL whether his water resistance was non-inductive or not, I think he
might have done so more easily by trying if at every moment the
ordinates of the current curve had a constant ratio to those of the
voltage curve. If this is not the case, the ^circuit is not non-inductive.
(Communicated) : The simpler method would, however, give no
indication of the value of the power-factor.

1903.]

AND FIELD: DISCUSSION.

771

Thornton.

Mr. W. DuDDELL : Mr. Campbell has pointed out that the two curves Mr. DuddcU.
should be exactly similar. Unfortunately, for watt meter measurements
where considerable accuracy is required, an error of one minute of a
degree is a serious matter in the lead or lag of the current through the
resistance. One minute of a degree is ^th of li^jth, or izjiiyTjth of a
half period. I do not think it is possible to plot a wave form with suffi-
cient accuracy to show a lag or lead of that order. I am afraid some
other method has to be used, such as employing a very high frequency
in order to determine such small angles.

Dr. W. M. Thornton (communicated) : It is to be regretted that Dr.
Mr. Field was unable to make observations at the generator end of
the cables, or on the high-tension side in the sub-station. There can
be little doubt, after comparing this and Messrs. Constable and Faws-
sett's paper, that the harmonics of Curve XV. are chiefly due to the
capacity of the cables ; but resonance is so violent and sudden a pheno-
menon that one is impelled to ask whether there may not be any other
explanation.

As I understand the method of experimenting, the curves were taken
from the low-tension side of a 175 k.w. transformer, unloaded. There
is then entering the cables the charging current together with a small
transformer current. But the secondary voltage of a transformer is
proportional to the primary current, and therefore any disturbance of
this by the distributed capacity of the cables will be inevitably felt on
the secondary side, though the conditions may be far from resonance.

According to this view, the greater the capacity of the cables
between generator and transformer, the greater would be the amplitude
of the harmonics on the voltage wave observed on the low- tension side
of the transformer.

The remarkable capacity currents caused by strong harmonics can
be seen by drawing the rate of change of the voltage against the gene-
rated wave : this representing the current to a suitable scale.

The intensity of the harmonics depends very much on excitation, and
one is led to ask whether the conditions of excitation were precisely the
same in Curves XV., XVI., XVII., XIX. They are widely separated in
time, and it is possible that all the conditions might not have been
repeated, especially if the tests were made in the early morning on a
very light load.

772

CONSTABLE AND FAWSSETT

[April 2ard,

Dr.
Thornton,

Mr.

Atchison.

With regard to the remark on page 655, that the field currents are
not much disturbed by armature reaction, I have found that a variation
of 5 per cent, is common in a separately excited three-phase bi-polar
converter, and I should think that in a multi-polar machine on full load
the effect would be even more marked on account of the relatively
smaller time-constant of the windings.

Harmonics in the voltage wave, on reaching the undisturbed
magnetic circuit of a converter, will reproduce the magnetic conditions
which started them. And if the iron is not saturated, the disturbance so
caused may be sufficient to increase the amplitude of the ripple in the
continuous voltage. This would account for the large ripples recorded,
and they should be larger the greater the angle of lag.*

On page 655 Mr. Field attributes the smoothing out of harmonics
when two or more generators are in parallel to the increased inductance
diminishing resonance. I made observations in the Wallsend power-
house of the Newcastle Electric Supply Co. two years ago which led
me then to believe that the obliteration of harmonics which ^^as alwa3rs
noticed when several generators were in parallel, was really caused by
difference of phase in the respective machines, for on tracing a wave
with strong harmonics, displacing it a few degrees from the original
and taking the mean, the harmonics in the resultant wave are much
less prominent. This small difference of phase may be the result of
variable turning moment and will then give rise to synchronising cur-
rents which usually reverse in time with the engine ; a change in
excitation of one of the machines in order to distribute the station load
as desired, will produce the same interchange of current which will
now, however, not change sign.

The commencement of Part II. deals with the growth and decay of
currents in large inductive circuits. I would refer Mr. Field to a
paper! read before the Newcastle Section last session, in which an
oscillograph was used for the same purpose, and where I gave a more
complete analysis of the curves obtained.

Mr. A. F. T. Atchison ( communicated) : Mr. Field's very interesting
paper brings before the notice of electrical engineers the existence in
practice of some phenomena which have hitherto been considered as
possessing chiefly theoretical interest. The oscillograph is an instrument
which opens out great possibilities for the investigation of phenomena
taking place in alternating-current circuits, and it is of special value in
revealing the many secondary effects which are ignored in the ordinary
mathematical treatment of the subject such as is given in the greater
proportion of our text-books. This treatment of alternating currents is,
and will always remain, one of the most striking applications of mathe-
matical analysis to practical work, but researches such as those of Mr.
Field and others, assisted by the oscillograph, serve to show that the
common methods of calculating alternating-current problems, though
correct in the main, are necessarily somewhat superficial and incom-
plete. One of the chief omissions in the ordinary theory is the neglect

• The Electrician^ Jan. 30, 1903, p. 609.
t /61V/., April and May, 1902.

THE NEW YORK

PUBLIC LIBRARY

-■* lFNO>

S* Mr.

^ Atchison.

. Mr. Mather.

Fig. K. — Capacity 90 m.f.

Fig. O. — 2725 m.f.
Exact Resonance vvitli 5th Harmonic.

Fig. S.— 3675 m.f.

Fig. L.

P.D. AND Cl'RREN'T OSCILLOGRAMS FROM .

ircuit.

19080

AND FIELD; DISCUSSION.

778

of the change in wave-form which may occur under certain conditions* Mr.
and which Mr. Field has brought before our notice in his admirable paper. ^ ^^'

The change of wave-form which may result from resonance with
high harmonics or " ripples " of the fundamental wave through capacity
of certain values existing in the circuit are very interesting, and are
shown very clearly by the oscillograph. The effects however may be
very much more important, when resonance occurs with lower
harmonics.

As an example of the great extent to which these harmonics may be
brought into prominence, I give a series of oscillograms taken (with a
Blondel double oscillograph) from an alternator working on capacity
loads of different magnitudes, bringing in marked resonance with the
fifth harmonic (or overtone of quintuple frequency).

The E.M.F. wave-form of the alternator on open circuit is shown in
Fig. U, containing pronounced triple and quintuple harmonics, and is
found to undergo but slight alteration on a non-inductive load. A
gradual increase of capacity, however, gives rise to the series of wave-
forms given in Figs. K to T ; very well-marked resonance with the fifth
harmonic taking place with a capacity of 27*25 microfarads in circuit
(Fig. O) ; the current during this stage being practically a simple sine
wave of 5 times the fundamental frequency of the alternator, each
component being naturally in quadrature with the corresponding peak
and hollow in the P.D. wave. A further increase of capacity destroys
the resonance, as would be expected, and the wave-forms become more
normal. Even at resonance with the fifth harmonic the rise of voltage
across the alternator terminals amounted to 43 per cent, (rising from
200 to 286), and had I been able to increase the capacity still further,
so as to bring about resonance with the third harmonic, no doubt the
effects might have been magnified to an even greater extent. The rise of
voltage is of course partly due to the fact that the machine is supplying
a leading current and is therefore working with a strengthened field.

It is interesting to calculate the value of the " apparent reactance "
of the alternator armature, from the value of the capacity which gives
rise to resonance. The frequency of the fundamental wave was 57 (\J
per second, and thus, taking 27*25 m.f . as the capacity corresponding to
exact resonance with the fifth harmonic, we have

2 T X 5 X 57 X 2725 X 10''

ohms

= 20'5 ohms at the frequency of the 5th harmonic
(5 X 57 = 285 oj per sec).

u., a reactance of 4*1 ohms at the fundamental frequency, which is not
very different from the value, 4*38 ohms, which was obtained from the
"open '* and " short-circuit characteristics " of the machine — the " Syn-
chronous Reactance " of the American writers.

Mr. T. Mather (communicated) : The best thanks of the Institution Mr. Matiicr
are due to the authors for putting such valuable data before its members.

774 CONSTABLE AND FAWSSETT [April Sard,

Mr. Mather. * The communications will, it is hoped, induce central station engineers
to pay more attention to the testing department of the works under
their control, with a view to locating and reducing the various losses
which inevitably occur in the distribution of electric energy. We may
also hope that further data as to losses in generation will be forth-
coming.

The paper is specially interesting because of the large number of
wave-forms met with in actual practice which it contains. These illus-
trate in a striking manner how the shapes depend on the load on the
station and on the feeders connected with the 'bus-bars. Another
valuable part of the paper is the section dealing with the measurement
of dielectric losses in cables ; and Table III., giving the " constants" of
the wattmeters employed in the tests, is instructive in showing how
much the so-called "constants" of such instruments may vary when
used under different conditions.

Every one who has attempted to measure power in circuits of low
power-factor with any approach to accuracy will appreciate the diffi-
culties met with by the authors in their efforts to obtain consistent
results, for the trouble rapidly increases as the power-factor decreases.

The Swinburne wattmeter behaved better than the Thomson instru-
ments, yet, according to the value in Table III., the " constant" of the
former decreased nearly 30 per cent, on changing from a leading cur-
rent, power-factor 0*129, to a lagging current of power-factor 0*034.
This would indicate that the pressure circuit was inductive, and I would
ask whether the instrument ever gave negative readings on any of the
cables tested ?

The change of " constant " here observed is quite moderate in
amount when compared with that shown by other instruments on the
market, and which claim to be non-inductive. One I tested some two
years ago gave results six or seven times as high as they should have
been on a condenser circuit, and about one-third of the correct value
on a chokei'. The true "constant," i.e., the number by which the
deflexions of the wattmeter have to be multiplied to get " watts," was
therefore twenty times as large in the latter case as in the former. The
wattmeter itself was fairly good, and the fault lay in the pressure
circuit resistance coils supplied with the instrument. These coils,
although wound in the way invented by Mr. Swinburne for minimising
induction and capacity, are decidedly anti-inductive, i.<?., the current
through the coils leads on the P.D. between the terminals. In fact the
lead was quite measurable by the contact-maker method at a frequency
of 100. On replacing the coils by another resistance of better design
the readings of the wattmeter became correct within a few per cent.

As Mr. Addenbrooke has referred to the measurements of dielectric
hysteresis by the aid of " air core transformers " (ironless chokers) made by
Professor Ayrton and myself in 1901, I take this opportunity of answer-
ing some of his queries. In the first place I agree with Mr. Addenbrooke
that the value of the power-factor for paper cables then published is
somewhat higher than the average for high-tension cables of that make.
I would also point out that although our measurements of power-factor
gave results far less than Mr. Mordey's tests, our low values were some-

1903.] AND FIELD: DISCUSSION. 776

what higher than the correct ones. One reason for this is that (as was Mr. Mather,
pointed out at the time, Journ, !.£,£,, vol. 30, p. 412) the cables tested
were intended for low pressures, but were tested at 2,000 volts. The
slope of potential in the dielectric was therefore greater than is usual
in high-pressure cables, and this usually means greater power-factor.
Another reason why the low value we gave is too high, is that the eddy
current loss in the choker was neglected in these tests, and this, as I
pointed out in the Electrician (March 8, 1901, p. 750), makes the power-
factor appear higher than the true value. This effect of eddy currents
loss is indicated on p. 413 of the Journal (vol. 30), for the tests made
without the choker. Fig. D, gave the smallest power-factor, viz., 0*023,
whereas those with the choker, Figs. B and C, gave 0*025. Mr. Adden-
brooke's estimate of the eddy loss in our choker, 60 watts, is, however,
too liberal. Possibly this is due to his taking the ampere-turns on the
coil as 12,000 instead of 8,000. A third reason for our low power-
factors being in excess of the correct values is found in the fact that,
although the coils used in the pressure circuit were the most perfectly
non-inductive resistances then made, they were slightly anti- inductive.
This caused the current in the pressure circuit to lead on the P.D., and
made the wattmeter read high on circuits taking leading currents. It
will therefore be seen that the numbers I pubUshed in 1901 for the
power-factors of paper, indiarubber, and jute cables, although only a
small fraction of Mr. Mordey's value, were actually higher than the real
ones.

Since 1901 I have, with the kind permission of Professor Ayrton,
tested other paper cables at 2,000 volts, using in the pressure circuit of
our wattmeter the improved resistances mentioned by Mr. Duddell in
this discussion ; the power-factors obtained varied between 0*015 and
0*019.

During his remarks Mr. Addenbrooke said one of the disadvantages
of using ** ironless chokers " in cable tests was the large capacity (three
or four microfarads), and therefore long lengths of cable, necessary to
produce resonance. In this connection I may mention a choker con-
structed at the Central Technical College two years ago, and referred to
in the Electrician of March 8, 1901 (p. 750). This coil has an induc-
tance of nearly 6 henries, and will balance about 0*4 microfarad at
100 f\j ; it contains i cwt. of No. 18 wire, and absorbs only 24 watts
at 2,000 volts. The question of a choker necessary to balance a small
capacity is, however, merely a matter of design, and there is no diffi-
culty whatever in making a choker suitable for testing 1 10 yards, or even
shorter lengths, of cable.

Considerable improvement in sensitiveness and accuracy has been
made in dynamometer wattmeters and shunt resistances during the past
few years, and it is now possible to measure the loss in short pieces of
cable. Twenty-yard lengths have been tested with comparative ease.
The currents taken by such lengths of small capacity cables were very
small, but were easily and accurately measured by shunting an electro-
static voltmeter with non-inductive resistances.

Tests have also been made (using improved apparatus) on con-
densers, with the result that the power-factor pf some Swinburne
Vol.. 82. 61

776

CONSTABLE AND FAWSSETT

[April 23rd,

Mr. Mather condensers were found to be below o*oo8, and of some condensers
made by the late Mr. Cromwell Varley more than thirty years ago below
0*004. For much assistance in these tests I desire to thank Messrs. Few.
Finnis, Nesfield, and Selvey, students of the Central Technical College,

It is of great interest and importance to notice that the condensers
made by Mr. Swinburne some ten years ago show losses very much less
than modern cables. This is highly creditable to our late President,
especially as the dielectric in these condensers is very thin compared
with that on high-tension cables, and the potential gradient in the
dielectric correspondingly great. As condensers can thus be made with
dielectric loss about half that of modern cables, it should be possible to
reduce the power-factors of cables to half the values now usual. Makers
of cables will doubtless give this matter their careful attention,
especially where extra-high-tension cables are concerned.

In connection with Mr. Field's paper I might mention a simple way
of detecting which harmonics are present in the wave-form of a machine.
This is to watch the ammeter in circuit with an unloaded cable (or
condenser) as the machine slows down. If any important harmonics
exist the reading of the ammeter, instead of falling gradually, will
remain steady, or even rise when the speed reaches a value which
causes any particular harmonic to resonate. With some machines
several rises may be observed before the alternator comes to rest*
The method may be made quite safe by introducing sufficient non-
inductive resistance in the circuit to prevent the rises becoming
excessive.

Mr. A. D. Constable, in reply, said : I have to thank you, gentlemen,
on behalf of Mr. Fawssett and myself, for the considerate treatment
which has been accorded to our paper, notwithstanding its short-
comings. Some of the inconclusive figures given in Table 4, with
regard to cable losses, would not have been placed before the Institu-
tion had it not been for the fact that it was impossible to continue the
experiments and further verify the results. The results were given as
obtained, and we hoped that they would be discussed, with a view to
deciding the causes of the discrepancies. I will try to treat the
various points raised as far as possible in the order they occur in
the paper. Mr. Minshall referred to the cost of lost units being very
heavy because the greater proportion takes place at times of maximum
load. It is true that about 60 per cent, of the loss occurs at times of
heavy load. That means in this particular case (where the total loss
is 22 per cent.) about 13 per cent, additional plant has had to be put
in to supply those wasted units, beyond what is necessary for the
maximum useful load. The whole annual cost of this 13 per cent,
extra plant must be put down to the units wasted during the time
it is running only, and although as a rule the actual running cost
is rather less during heavy loads than during the day, the total
cost may, therefore, be high. In certain cases also, where it is
necessary to run an additional generator owing to the day-load losses,
these will cost more than the average per unit generated.

Mr.
Constable.

* See Electrical Review, May 31, 1901, pp, 915-917.

1908.]

AND FIELD: DISCUSSION.

777

A question was asked about Table i. This Table includes the losses
from the generator terminals to the feeder terminals. The percentage
(o'S) is small, but it represents an expenditure of about ;£8o per annum»
so that if ;f 200 or ;f 300 additional capital outlay would save, say, one-
third of the loss, it would be worth while spending it.

Mr. Duddell's objections to diagrams 3 and 4 are unfounded, as he
hopes. We had a large non-inductive resistance in series with the
pressure coil of the wattmeter in all
cases, and also in series with the volt
coil with the oscillograph, but it is
omitted in the diagrams. The total re-
sistance of the wattmeter shunt circuit
was about 7,000 ohms, so that the pres-
sure coil is taking rather less than i per
cent, of the total current in the resistance
R,, Diagram 3. In connection with
Diagram 3, Mr. Duddell asked how we
obtained the power-factor with a leading
current I will try to explain this by
means of a diagram.

Ra is a Don-inductive resistance in series with the wattmeter current
coil, and the ciu-rent in it, A^, is in phase with the applied volts, V.
C is the ironless choker with resistance, R, and in series with it is the
non-inductive resistance, R,.

The wattmeter pressure coil is connected to the terminals of R„
the voltage across which is V. A, is the current in C and R,.

V is in phase with A„ and since A, lags behind V, the current A, is
leading with regard to V.

The watts absorbed by the choker = A,* R,

Mr.
Constable

Fig. v.

= A.V;

the total watts in the choker circuit therefore equal A, (A, R + V), the
corresponding volt-amperes = Ax V; therefore the power factor of the

choker circuit is equal to -^} -^r- — ' = cos 9, where 9 is, by the usual

definition, the equivalent angle of lag of Ai behind V.

The watts indicated by the wattmeter will be AaVK cos $, where
K = constant of instrument, so that —

K=:

Reading _ Reading X V /R.M.S.\
A, V cos 9 ~ K (A, R + V) V \ values/*

If now we are not dealing with sine waves, the voltages across C and
R, respectively may be different functions of the time, so that A, R and V
cannot strictly be added, but with the wave forms used in the calibration,
the error tjjus introduced will be very small.

[Note added later, — I am now obliged to admit, on further con-
sideration, that the possibility of errors being introduced by accepting
this calibration may be greater than was at first supposed. In reply
to Mr. Mather's query, I may say that the wattmeters used in our
experiments did not at any time give a negative reading on the cables
tested.]

778 CONSTABLE AND FAWSSETT [April 23rd.

Mr. It is true that the calibration is only quite correct for the particular

** wave forms used, and in the cable experiments the wave forms were
sometimes very diflFerent. We do not profess that all the figures in
Table 4 are absolutely accurate, but what we attempted to show and
tabulate in Table 3 was that the wattmeters gave an approximately
correct reading for both lagging and leading currents and for cousider-
ably different wave forms. We agree with Mr. Duddell that the watt-
meter method is by far the best to obtain the power factor in a cable if
a wattmeter can be obtained which will indicate watts only and not
concern itself with several other things as well. I am glad to hear that
such an instrument has been devised by Mr. Duddell. The motor
alternator method might be of use, but it is rather complicated and
requires a number of simultaneous readings and adjustments to make
it practicable. Mr. Mordey rather advocated the calorimetric method,
which certainly cannot be used after the cable is laid, and if the cable is
coiled in a tank inaccuracies are introduced, as Mr. Minshall has found.
The method might be used if a specially lagged trough were made, of
considerable length, as suggested by Mr. Mordey and Mr. Minshall, and
the temperature rise in a given time measured ; but even in the worst
cable, No. 7, the watts lost per yard are only about 06, so that there
would be some difficulty in measuring the temperature rise accurately
in an iron trough, such as should be used.

Mr. Duddell's vigorous criticism of Table 4 was perhaps justified
by the appearance of some of the figures. We do not profess that
these figures are all even approximately accurate. Where great
discrepancies appear, the figures are inserted to show what diver-
gence may occur even in experiments made with care. Cable No. 7
is without doubt abnormal, while the variations in Nos. 4, 7, and 9
are hardly larger than would be expected from the conditions. Cable
No. 10 is an exception. Of the two very different values obtained fcM*
that cable, the second, namely, 0*024, was obtained with the choker
in parallel with the cable, and is therefore probably the more accurate.
The low insulation, 2 rCt, is due to switch base leakage, and not to the
cable. In the case of experiments i to 13 the figures are the means of
several sets of readings. The frequency in all cases was 60 r\j , within
I per cent. With regard to cable 11, Mr. Duddell accused us of
arbitrarily selecting results and of failing to draw the proper inferences
from the experiments. The reason for selecting experiments 18 to 20
in preference to 15 to 17 are given in the paper on p. 716. These
experiments were made with different machines. Nos. 18 to 20 were
taken with a 120-kw. machine, whilst Nos. 15-17 were taken with a
30-kw. machine of the same type, and there was no other difference to
account for the former being the much smoother waves. It is prac-
tically impossible to work out oscillograph curves when th^ waves are
very peaked, but the results of the smoother waves should be fairly
accurate, though we do not suppose that either result is quite correct
Unfortunately we had no suitable wattmeter available at the time, and
there has been no opportunity of checking the results since. As to the
effect of the wave-form on hysteresis loss, we prefer to judge by the
majority of the experiments, which show there is npt §uch a great

190S.] AND FIELD : DISCUSSION. 779

difference as experiments 15 to 20 indicate, although there is some Mr.
variation. Mr. Duddell also remarked on the low result obtained for
the watts absorbed by cable 12. We only obtained 900 watts, whereas
the figure should have been about 1,100, summing up the watts
absorbed in the various component parts, after correcting for voltage.
But again this experiment was made without a wattmeter, and so there
is a good deal of possibility of error in working out the results.

Mr. Field questioned Table 5. In that table the figures in the last
column were calculated from data obtained by experiment. We took
the readings on cable No. 7 and observed the watts absorbed, but as
this was an abnormal case, we wished to correct them for a hypothetical
paper cable. The results are therefore only approximate, as stated. Our
experience goes to confirm Mr. Field's remarks to the effect that a
dielectric with a high hysteresis loss has a low disruptive strength.
With regard to the magnetic field stated to exist round a cable, since
writing the paper we have made some further experiments. A large
alternating current, 250 amperes at 60 C\J , was passed through the
inner and back by the outer of 50 ft. of cable of the type of No. 11,
Table 4, in a straight length. At the centre a piece of cast-iron
trough 6 ft long was placed. Three feet of the trough had the cover
removed from it. A search coil 18 in. by 5 in., consisting of 200
turns of fine wire connected to a telephone, was fixed (at the same
distance from the centre of cable) (A) over the uncovered portion
of cable, (B) over the uncovered portion of trough, (C) over the
covered portion of trough. In position (A) the noise was very loud,
at (B) it was much less, and at (C) there was practically silence.
The noise in position (A) was roughly the same as that produced
by a current of 2 amperes in a long straight wire at the same
distance from the coil (about 2^ in.). That seems to show that there is
an external magnetic field which is practically all shielded by the iron
trough. A piece of concentric armoured cable behaved in the same way,
but the shielding effect of the thin armour was slight. Cable 7 has the
outer conductor of a rather open strand, so that the external field may
be greater than in the case of No. 11, which has a closely laid outer.
(It is difficult to see how this field can exist, liowever.) It will be of
interest to pursue these experiments and investigate the strength of field
in the iron trough kt ordinary loads. It still appears possible that some
of the apparent dielectric hysteresis loss is really iron loss in the case
of No. 7 cable.

Mr. Mordey stated he thought it was more economical to allow
several transformers to share the load than to keep one or two fully
loaded. We admit that. Our point, however, was that it was very
wasteful to keep many transformers on at times of no load, and these
times make up the greater part of the 24 hours.

Mr. Andrews referred to the danger of switching off transformers.
I may say that during six years not one of the fifty odd transformers in
Croydon has broken down due to repeated switching off and on. That
they are all of the oil-cooled type may be partly responsible for this.
Small punctiu'es in the insulation, if they exist, may be filled up with
oil before the transformers are again used. The oil, too, will act as a

780 CONSTABLE AND FAWSSETT [April 2Srd,

Mr. lubricant and prevent abrasion of the insulation due to vibration and

alternate expansion and contraction. The mean temperature of the
transformers is kept down by the practice of switching off transformers
not required. With reference to the remarks on meters ; in direct-
current systems, ampere-hour meters of considerable capacity are
obtainable which will record accurately on a 200-voIt 5-c.p. lamp. If
there are no very satisfactory alternating-current ampere-hour meters,
it is possible to obtain accurate energy meters which require an
exceedingly small shunt current and which have no moving contacts.
Meters which require frequent inspection, cleaning, and adjusting
cause more than half the trouble between the supply authorities and
the consumers.

Mr. Addenbrooke has mentioned that the loss in a cable increases
more than proportionately to the rise in voltage. We have found that
to be the case ; in fact, in some experiments we made, the increase has
been more than proportionate to the square of the voltage. I am
glad to hear that Mr. Addenbrooke also finds a considerable increase
in the loss when the cable is surrounded by iron. Mr. Sparks men-
tioned the dangers of running up an alternator on a cable slowly.
That is illustrated by curve 13, sheet C, in the paper. There we
had an alternator running at about half speed under otherwise ordinary
conditions on a cable, and the voltage rose to about 6,000 maximum
on a 2,000-volt system.

I do not think any other points raised remain to be dealt with, and
will therefore conclude my remarks by again thanking you for your
kind reception of this paper.

[Note added later. — In all cases the C'R loss due to the capacity
current is included in the dielectric hysteresis loss, its value being only
a small percentage of the total.]

Mi. Field. Mr. M. B. FiELD {in reply) : - I think the best way to answer the many

remarks that have been made upon my paper will be to deal first with the
more direct criticisms, and after that to cover with a few general remarks
the further comments of other speakers. Referring first to Professor
Hay, I certainly grant that to be lax with one's terminology is a most
serious error for any one to fall into, and perhaps I am to a certain extent
guilty in this respect, but I think that Professor Hay Ijas rather exagge-
rated my delinquencies. First, with regard to the secohm. I supp>ose
I should not defend the term, as it has now, by universal consent, been
discarded, but it seems to me such a rational term, and " henry"
seems anything but that. " Secohm " gives one at once an idea of what
it is. Coefficient of self-induction may be said to be defined by the
usual equation —

V = RC -h L"^

and is really the back E.M.F. in volts in a circuit when the current is
altering at the rate of i amp. per sec. As regards its dimensions L is

* Mr. Field's reply to the discussion on his paper at Glasgow (see p. 694)
is included here.

1903.] AND FIELD: DISCUSSION. 781

and therefore of the nature of a time multiplied by a voltage Mr. Field.

v^M

/C
and divided by a current, hence the term sec-ohm.

Ohmic Resistafice : The adjective " ohmic " may be superfluous, but
no one can call it misleading. I use it to distinguish resistance-proper
from "apparent" resistance, with which the paper deals considerably.
I have referred to certain combinations of self-induction and capacity
as behaving, as far as the external circuit is concerned, as a resistance
of so many ohms. This is, of course, only an apparent resistance, as in
most cases it is only true at one particular frequency that the combina-
tion could be exactly replaced by a resistance. In dealing with such
combinations I maintain thut it is not at all out of place to draw the
distinction between resistance-proper and apparent resistance by
applying the epithet " ohmic " to the former.

Self-induction of an Alternator: Professor Hay states I have used
this term in more than one sense. I consider I have been most careful
to explain the exact sense in which I have used it. I have pointed out
what I consider the distinction between self-induction and armature
reaction is. I have pointed out that an alternator cannot strictly be
said to have any true coefficient of self-induction, as this depends on,
and varies with, the saturation of the field-magnet system, the position
of same relative to the armature coils, and the strength of the armature
currents. I have pointed out the variable nature of this coefficient ; I
have then for shortness included in the term "self-induction" the
effect of armature reaction, saying, " In talking of the self-induction of
an alternator I shall, for the purpose of this paper, include in the term,
armature reaction, i.e.^ I shall refer to that self-induction (whether with
constant or variable coefficient) which, inserted in series with a
reaction less and self-inductionless machine, would give the same
characteristics." Surely I cannot be blamed for indefiniteness here.

Synchronous Impedance : This is an American term. I think it
implies \yhat it is, viz., the impedance at synchronous speed. It
includes self-induction and armature reaction, being determined by
the comparison of the short-circuit armature current at synchronous
speed at a given excitation, with the no load E.M.F. at same speed
and excitation. The term is quite a well-known one.

I was somewhat surprised at the rather dogmatic way Professor
Hay denied the correctness of the

statement on page 662 that the ^ a ''

combination (Fig. W.) behaves under pRRRmnn — vww^^

all conditions, as far as the external ^i (=^ aaaaaaJ^*

circuit is concerned, as a resistance k ^ ^

of r ohms provided K = ^^ The ^»^- '^'•

text may be a little badly worded here, but when I say that this is true for
all frequencies and for periodic and unperiodic functions, it is perfectly
evident that the condition represented by (9) which refers to one particu-
lar frequency, has nothing to do with the matter. I did not attempt to
prove my statement because the proof is to be found elsewhere. I
thought it was a matter of common knowledge, for certainly Professor

782 CONSTABLE AND FAWSSETT [April 23rd,

Mr. Field, Perry has been in the habit of giving this case as an example to his
students for fourteen or fifteen years. The proof is to be found on
page 247 of Perry's "Calculus." This combination is, however, interest-
ing from many points of view, and is worth study.

In the first place we see that if energy be stored either in the self-
induction or the capacity, and this be allowed to discharge in the
closed circuit, the combination is the critical one at which the dis-
charge just ceases to be oscillatory.

Secondly, however V may vary, the total energy stored in the seK-
induction at every instant is equal to that stored in the capacity,
for remembering L = K r* we may write, using Professor Perry's
symbol 9-^

V = r(i -h Kre)C,

-i'+K-y-

The energy stored in the self-induction at any instant is 4 L C,* ; and in
the capacity i K ( V — r C,)'. But it is clear that both these expressions

may be written in the form —7 — ; jr-nrz . V' ; hence, however V may

have varied, the total energy stored at any instant as expressed by this
formula is the same both for self-induction and capacity.

It is further interesting to note that if current be flowing through
the combination from the external circuit so that a certain amount of
energy is stored both in the self-induction and the capacity, on
suddenly interrupting the external circuit, although the stored-up
energy will discharge itself in the closed loop, there will be no differ-
ence of potential between the points a and b. Professor Gray has
pointed out an error I have fallen into where, on page 668, I determine
the coefficient of self-induction of an alternator (working under certain
conditions) by taking the slope of the synchronous impedance curve.

I have really assumed that the equation V = R C -f L -r-. still holds

for a circuit containing iron (and therefore with a variable coefficient
of self-induction) provided we express L in the above equation as a
function of C. Professor Gray's criticism is quite justified. The true
equation should be —

V=RC + ''M

o, V-RC + L^jf + C^jt

that is to say, I have left out of account this last term. As, however, I
have based no calculations on this, the drift of my argument is not
affected.

Professor Carus- Wilson has found fault with some of my mathe-
matics, asking whether the minus signs on page 691 in the expres-
sions for Vo should not be positive signs. Several of the professors
have pointed out that the mathematics of the subjects treated in my
paper have been worked out before. It is hardly necessary for me to
say that I am perfectly aware of this, and have stated so myself in the

1903.] AND FIELD: DISCUSSION. 783

paper, and for this reason I have avoided mathematical treatment as Mr. Field,
far as possible. The theory of electric oscillations in capacity self-
induction circuits was first worked 'out by Lord Kelvin between fifty
and sixty years ago. In Part IL I have therefore merely stated the
general difiFerential equation which holds for such a circuit, and then
given the particular solutions applicable to the cases experimentally
investigated. (I have, it is true, as a slight digression, discussed briefly
the characteristics of the damped oscillations, to remind those readers
unfamiliar with the subject.) Professor Carus- Wilson has referred to
Mr. C. P. Steimnetz's paper on this subject. My attention was called
to this after my own was mostly written. Mr. Steinmetz in his
admirable work treats the whole subject more as a mathematical
problem. I must say I found the paper rather long and difficult, and
the more important conclusions arrived at by making certain simpli-
fications at the end of the work, I have tried to compass without the
mathematics. With regard to Part IIL, Professor Carus- Wilson has
referred to the work of Houston and Kennelly. These, of course, are
not the only writers on this subject, e,g., C. P. Steinmetz, Bedell, and
Crchore, etc., and I think that the work of even these writers is to a
certain extent an adaptation of Fourier to electrical problems similar
to the heat problems treated mathematically by that physicist. Being
again fully aware of this, I have satisfied myself with stating merely
the general difiFerential equations, and the particular solutions applic-
able to the case I am considering, viz., resonance at the end of a long
unloaded three-phase cable, due to a high order of harmonic, which I
have shown may exist in a practicable alternator, and my intention has
been to arrive at the conclusion, by means of a numerical result, as to
whether such resonance is likely to prove dangerous or not.

Coming now to Professor Carus- Wilson's query re positive and
negative signs, perhaps the best way will be for me to show here how
the expressions in question are arrived at : —

The solutions given in the paper for v and c are (see page 689) —

r = V, [f-^sinCairw/ — aA:-h^)H-c-^"'-'^sin(2irn/ — a(2/ — :r)H-^)]

c = etc.

a = etc (i)

These equations can of course easily be verified by difiFerentiation.

We see that when a: = /, c = o, which is the condition of an
unloaded cable ; V, and ^ are arbitrary constants, but if we say that at
the beginning of the cable we will define the voltage as V© sin 2 «• n /,
we can find V, and ^ as follows : —

Inserting in{i) x =^ 0

VoSin2irn/ = V, [sin{2irni + ^) -f €-"'sin(2irn/ — 20/ + ^)]
Let 2irii/-f^=so, then

VoSin^ = V,c-"'sin2a/ (2)

Lct2ir«/-f^ = -, then

VoCos^ = V, (I -h €-'»'cos2a/) (3)

784 CONSTABLE AND FAWSSETT [April 23rd,

Mr. Field. Dividing (2) by (3) we have

tan0 = ^_^_,^,

_r-'^ sin 2 a /

I + (-'^^ cos 2a I

Squaring (2) and (3), adding and taking the square root, we have

Vo = V, s/r^- €-•♦-' + 2 c-'^' cos 2 a / (4)

I then state that maximum resonance will occur when a / = - . the rise

of voltage occurring at the free end of the cable. Inserting in (i) at = /,
/ = — , we have as the voltage at the far end

2 V, I € 2 a sin ^2 v« / + ^ — -j J
the maximum value of which is

w a
2V,€ 2 a (5;

combining (4) and (5), and remembering that ^ = tan 0, we have the

expression

- ' tan » - '^ tan <?

,— ^-'^l--^-^-_^Vo or J'i-l V,. . (6)

^ I _j_ f- 2 5r tan ^ ^ 2 e"'' ^^" ^ I ^ €~^ tan 0 ^ '

These are the expressions to which Professor Carus- Wilson objected,
asking whether the minus sign which I have shown in thick type
should not be positive. I would point out that whether this sign is
positive or negative entirely depends on the term cos 2 a / in (4), and

hence on the length of the cable under consideration. Where / =

^ la

the case here considered cos 2 a / = — i, where / = , cos 2a/ = + i.

This latter case, however, viz., where the length of the unloaded cable

equals one half of the wave length is not a condition of resonance.

With the correct length to give rise to resonance, the E.M.F. at the

free end will be greatest when the copper resistance is smallest. If we

assume this becomes vanishingly small, tan 9 = 0, and the voltage

at the free end of the cable is for / = — , infinity; and for / = -, Vo;

2a "^ a

that is, in this case, the voltage at both ends of the cable is the same.

This hypothetical case of a length of cable equal to one quarter
wave length where the copper resistance is negligible is of great
interest. Mr. Steinmetz has pointed out that at the one particular
frequency it behaves as a constant potential to constant-current trans-
former, i.e., if constant potential be maintained at one end, constant
current will be given out at the other irrespective of the nature of the
load (except, of course, in the case where the cable is an open circuit,
when the potential rises to infinity, as above.) That this must be so is
evident from the equations for v and c ; for however the cable is loaded

1903.] AND FIELD: DISCUSSION. 785

the same form of expression holds for the current at one end of the Mr. Field
cable as for the voltage at the other, and vice versd^ the coefficients
only differing ; hence if at one end the voltage be maintained constant,
at the other end the current will remain so, and vice versd:^'

I do not altogether agree with Professor Carus- Wilson in supposing
that this class of resonance will never be dangerous. Suppose an E.M.F.
represented by the wave Curve XV. were applied to such a cable as I
have assumed in my calculation, and the 13th harmonic were trans-
formed up twelve times. At the far end of the cable the harmonic
might quite easily be twice as important as the fundamental, in
^^hich case the maximum voltage would be nearly three times that
of the fundamental.

Messrs. Constable and Fawssett in their excellent paper indicate that
they expected to find a change of wave shape at different points along
a fairly long cable, unloaded, upon which they experimented, and
expressed surprise in failing to do so. I think myself that the length
of cable necessary before any appreciable change would be observed
is far beyond anything they have at Croydon. I do not think either
that a change of frequency (within reason) would have created the
expected variation as supposed.

In this connection I think it will not be altogether out of place here
to ^ve a comparatively simple graphical method for determining the
current and voltage at any point of a long cable loaded on a more or
less inductive circuit. Clearly we need only consider one harmonic or
a sine function of E.M.F., for however complicated the apphed E.M.F.
may be, each term of the Fourier's series into which it can be expanded
may be treated in like manner.

In the first place it is clear that the solution given on page 689
becomes for a loaded cable

T» = W** sin (2 x« / — a;rH-0') + V"€-*^^'-'>sin (2 Tw/ — a(2/ — :r) + ^")

V"
+ 0)-—.

c=:— f-*' sin (2 7r/j/ — a^r-l-^' + 0) f-=»r»/-'^ sin(2x;i/ — 0(2/ — x)

where

I 2'jrnK

= ,_ or

V 2 TT W ^

• In this connection my brother, A. B. Field, has pointed out that the
following combination of self-inductions and capacity acts as a constant
potential to current transformer, provided it is loaded on a non-inductive load,

and n is such that 2 7rw = v f-rv ; the proof is simple ; the combination is
^ 1^ K.

very interesting. I understand that Mr. Steinmetz first called attention to this

combination.

Fig. X.

786

CONSTABLE AND FAWSSETT

[April 23rd»

Mr. Fidd. and whcrc V, V", \l/', yjf" arc determined by the terminal conditions—

X ss: Of V ssVo sin 2 nnt; jr = /, c =

('+'!,)

v/ being the value of v, obtained by putting in the value a: = /, and r
and / are the resistance and coefficient of self-induction of the circuit
external to the cable, hereafter termed "the external circuit." Let the
impedance of this circuit or Jr' + 4ir'n'/' be denoted by T. We see
that V and c consist each of an original and a reflected wave, and that
the phase of each wave at any particular instant changes uniformly as
we go along the cable. The difference of phase at two points separated
by the distance a; is w where ut s= ax, whereas the ratio of the ampli-
tudes at these points is c- tan # if^ now, we draw a logarithmic spiral,
r ^= c«tan(?(see Fig. Y), of which the co-ordinates are r and w, and

say that the radius O a represents
in magnitude and phase the original
wave at the far end of the cable,
then O^ will represent the magni-
tude and phase at a distance x, from
the end, where w, = «*i. Similarly
if O a' represent the reflected wave
at the end of the cable, Ob' will
again be the phase and magnitude
of the same at distance x^ from end.
The conditions which obtain at the
end of the cable are these : Let O V,
Fig. Z, be the voltage, and O c the
current. I have shown these in two
distinct diagrams for the sake of
clearness, preferably they should be combined in one. O c = O V/I'
and cos % is the power factor of the circuit supplied by the cable. Now
O V is the resultant of two waves, say O ti and O e ; corresponding to
each of these is a current wave, of which the amplitudes are O dly, O e/y,
and each is in advance of the corresponding potential wave by the
angle 0. The resultant oi O d and O ^ is O V, while the difference of
the two corresponding current waves is O C. This is evident from the
form of the equations v and c.

Draw a line O P, set back from O c by the angle 0. Bisect O V and

draw through the centre a line parallel to O P of length O V . J'j, so that

this vector is in its turn bisected by O V. Complete the parallelogram,
of which these vectors are the diagonals, then Od, Oe, represent the
two voltage waves, because they give a resultant OV, and when we
draw in the corresponding current waves in the current diagram, or
O d\ O e', these are such that (by construction) O rf' — O <?' = Oc.

We have now only to superimpose the logarithmic spiral on the top
of each diagram, rotate O rf, O ^ forwards through the angle J (=z at)
and O ^, O ^r' backwards through the same angle, increasing or decreasing
the magnitudes of these vectors in proportion to the value of the polar

Fig. Y.

1903.]

AND FIELD: DISCUSSION.

787

co-ordinate of the spiral, to find the values of the original and reflected Mr. Field
voltage and current waves at the beginning of the cable. Taking the
resultant of the two voltage vectors and equating this to Vo sin 2 irn /
we fix the scale of the diagram, and the datum from which time is

measured. For example, suppose al= we rotate O d forward through

a right angle and increase it in the proportion O s' : O s, we rotate O e
backwards through a right angle ancl decrease it in the proportion
O t : Ot, These two vectors represent the magnitude and phase of the
original and reflected waves at the beginning of the cable. Their
resultant is O Vq. Since the applied E.M.F. is Vo sin 2 x n / the length
OVo represents the voltage Vo which fixes the scale of the diagram,
while all phase relations of currents, voltages, etc., are referable to
O Vo. It is thus clear that by determining the values of the original
and reflected waves and taking the sum or difference as the case may be,
the true value of voltage and current at any point of the cable may be
determined.

Fk;. Z.

Professor Carus- Wilson asked for a further explanation of the footnote
on page 688. I thought this was sufficiently clear. pXx of Part III.
have entirely different dimensions from RLK in II. The latter are
resistance, self-induction, and capacity respectively, the former are
the same physical quantities divided by a length, or resistance, self-
induction, etc., per unit length. In Part II. v ,-j^ is a frequency, or of

the dimensions of T-' : in Part III. \/ ^-^ is a velocity or -7"- :

^ XK ^ time

it was to keep this distinction clearly before us that I resorted to the
Greek letters in Part III.

I do not agree with Professor Carus- Wilson in his remarks re the mis-
application of the term resonance, nor do I think that Houston and

Kennelly were the originators of the term. Resonance was known and
understood in other branches of physics, vide Helmholtz's Resonators
(accoustic), long before Houston and Kennelly's paper. One may say

788 CONSTABLE AND FAWSSETT [April 23rd.

Mr. Field. that the best definition ol resonance is " Synchronism between the
natural and forced vibrations of a system." With this definition the
phenomena investigated in Part I. are true resonance effects. We are
dealing with combinations of capacity and self-induction which have
a definite periodic time of their own (natural vibrations), if now the
frequency of the supply (or forced vibrations) correspond with the
natural, we get serious magnification of the amplitude of the vibration
or resonance. As another example, the periodic time of the vibrating
portion of the oscillograph is say, Ttriwath of a second, suppose we
passed an oscillatory current of the same frequency through the strips
we should have a case of mechanical resonance, the amplitude of
vibration being largely in excess of that which would normally cor-
respond to the current flowing. This is resonance in the strictest sense,
and Professor Carus-Wilson is unduly limiting the use of the expression in
restricting it only to such phenomena as are dealt with in Part III. In
Part II. I grant it is hardly in order to apply the term " resonance " to
the phenomena discussed, as there we are only dealing with the natural
vibrations, but I have pointed out on page 682 that while in Part I. we
have been dealing with cases wherein the frequency of the supply
synchronised with the natural oscillations (or frequency of supply

= -— V^:p^), in Part II. we are dealing only with the natural

oscillation, the frequency of which is the same as the above, viz.,

— ^ |-^. We may almost consider the latter case as a particular

instance of the former, where the amplitude of forced oscillation is
zero. At any rate, the laws governing the two cases are so similar
that I have classed the latter, though possibly incorrectly, as a
resonance effect.

Professor Maclean (Glasgow) has contributed some very interesting
remarks re harmonics present in some of the wave forms I have
reproduced. It is quite evident that in a three-phase Y connected
generator the 3rd, 6th, 9th, etc., harmonics can have no existence.*
If, however, the voltage wave between one terminal and the neutral
point had been reproduced (Le,, of one leg of the winding only) I fully
believe that traces of the 3rd, 9th, 15th, etc., would have been found.

I have pointed out that in such a generator the only harmonics
which can exist (voltage being taken between two line wires) are given
by the expression 6 w ^i i, where n is any whole number. If we give n
a value equal to the number of slots per pole per phase we get the two
harmonics, which will in all probability be the most predominant. In
the curves under examination we should expect to find only the 5th,
7th, nth, 13th, 17th, 19th, etc. Similarly with regard to the ripple in
the rotary D.C. E.M.F., as Mr. Hird has pointed out, the 5th and 7th
will produce a ripple of six times the normal frequency, the nth and
13th of twelve times, and so on ; hence the order of ripples will always
be a multiple of six.

• I have to thank Dr. J. B. Henderson of Glasf^ow University for first
calling my attention to the fact that on theoretical grounds these harmonics
must be non-existent in the alternators under discussion.

1903.] AND FIELD: DISCUSSION. 789

It is to be observed that since the nth and 13th harmonics will Mr. Field.
both produce a ripple in the D.C. E.M.F. of the rotary of twelve
times the normal frequency, these may either neutralise or aug-
ment each other. The cases are therefore possible that a large
ripple may appear !h the D.C. E.M.F. due to relatively small
harmonics in the A.C. wave, or again, a perfectly straight D.C.
E.M.F. line may result from an A.C. E.M.F. wave having consider-
able harmonics. The same thing of course applies to the other
pairs of harmonics. Professor Maclean has drawn attention to the
existence of a considerable 5th harmonic in certain wave forms.
The somewhat rough and ready explanation I have given on page 657
of the cause of the existence of the nth and 13th harmonics is based
entirely on the number of teeth in the armature. I point out that there
are twelve teeth per period, therefore we might expect twelve irregu-
larities in the magnetic curve, hence the reason for considering the
magnetic curve represented by F N sin Jfe / -f a (i — cos 12 ife /), etc. ;
following out the argument of the paper it would of course have
been incorrect to assume an expression such as a (i — cos 6kt) as
Professor Maclean indicates. On the other hand, the existence of a pro-
nounced 5th harmonic may very readily be imagined as due to the
crowding together of the copper in the armature. It is quite con-
ceivable that if the machine were a smpoth-core alternator, but with
the copper crowded together in the same way as in the actual case, a
5th harmonic might be the result. It is to be regretted that Professor
Maclean had not time to continue his analysis of the curves published
and determine in what proportion the 13th was present.

Coming now to Mr. Duddell's remarks, I would say in the first place
that I am quite aware of his beautiful photographic contrivance for
obtaining a continuous record from the oscillograph, but I could not
use it on the score of expense. The makers quoted me something like
£^0 for the apparatus, and I understand that it is a comparatively easy
matter to reel off £xo or ;£i2 worth of films in a few minutes.

I therefore resorted to the dark slide shown in the paper ; these
cost me about 30s. a piece and id. per exposure. Of course, I was
dealing with periodic effects, and those effects which were not really
periodic I made periodic by employing the contact maker already
described. I consider I obtained excellent results with my dark slides,
and I can strongly recommend the use of the same for similar work.
Where, however, it is desired to study such effects as those when arcs
break out, etc., I admit there is no way of doing it satisfactorily except
by the very expensive continuous film device.

Mr. Duddell referred to the effect on the A.C. voltage of a rotary,
of sparking at the commutator, and stated that he would not like to say
what might happen on account of resonance on the A.C. side should
this sparking become bad. I have myself observed similar effects pro-
duced by sparking, not on a rotary, but at the contact breaker already
referred to. I do not think, however, that this is likely to give rise to
dangerous oscillations in the cable system. It appears to me that there
is just as much likelihood of such effects occurring on the D.C. side as
the A.C., and if they are serious, some such effect would have been

790 CONSTABLE AND FAWSSETT [April 23rd,

Mr. Field. noticed and recorded before this in connection with sparky D.C.
generators which supply considerable cable networks. In the paper,
however, I have called attention to the possibility of resonance
with D.C. machines due to slight periodic voltage fluctuations
corresponding to the number of armature slots or commutator seg-
ments, e,g.j compare ripples on Curve IV. ; and although resonance
under these circumstances would not probably assume any very great
dimensions I think that in the case of rotary converters the e£Fect due
to the accentuated ripples in the D.C. voltage illustrated in the paper
might become very serious.

Attention has been drawn by several speakers to the danger in
running up a generator to full speed, when already excited and con-
nected to a cable system. This is a point I attach considerable
importance to and have dealt with myself in the paper. We did
not appreciate the fact at first at all at Glasgow, but nevertheless
noticed a curious effect during the process of starting up and shut-
ting down. At a certain speed or speeds, as mentioned by my former
assistant, Mr. S. Blackley, a kind of static sparking was observable
between the live metal portions of the Westinghouse high-tension
breakers into the wooden arms on which they were carried. It was
afterwards found that these eflFects corresponded with the critical
speeds at which partial resonance occurred.

Mr. Duddell referred at some length to the form factor ; he
attaches very great importance to the strain put upon the system due
to a high form factor. In my paper I have said it is a mistake to attach
too much importance to these eflFects, and to get frightened at them,
though I most strongly urge the advisability of every engineer investi-
gating fully what is going on inside his system so that he is in a position
to appreciate and overcome any difl&culties which may be introduced
thereby. I may say, however, that at Glasgow, with the exception of
the one isolated case above mentioned, there was nothing to indicate
that anything abnormal was occurring at aU. It was only because I
expected to find deformations of wave shape from theoretical consider-
ations that I was led to search for the results here published, and I may
say that in some instances a very considerable amount of experimenting
was necessary before I found the critical conditions.

When I was recently in the States I made a special point of asking
central station engineers whether they experienced difl&culties in work-
ing from these causes, and the almost invariable answer I received was
that but for the theoretical writings of certain authors they would not
know that such phenomena as resonance existed at all. Of course I
know that certain stations over here have had considerable trouble with
cables and apparatus, but nevertheless I am inclined to think that with
modern up-to-date systems of cables and apparatus there is not much
to fear. As regards form factor, even with a very distorted wave such
as Curve XV., it does not exceed 2 or 2*2, whereas the form factor of a
sine- wave is 1*4, i.e., the maximum E.M.F. in the former case is only
about 50 per cent, greater than in the latter, and if the insulation of the
system won't stand this the sooner it breaks down and is taken out the
better.

1903.] AND FIELD: DISCUSSION, 791

Another reason why I urge that too much importance should not be Mr. Field,
attached to the form factor is this : At the last meeting I indicated that
unless very excessive voltages be applied there is strong probability that
the determining factor as to whether an insulating material will break
down or not is the heat developed per unit volume and the actual
deterioration of the material thereby caused. If this be so, it is the
R.M.S. of the voltage wave we have to consider and not the form
factor. I do not wish to be misunderstood here ; if it is a question of
the insulation breaking down due to sparking across some air-gap or the
like, I do not dispute that it is the form factor we have to look to, but
what I mean is, if we consider a moderate excess of voltage which will
not instantly break down the insulation, but after, say, 5 or lo minutes,
or even half an hour, then the primary cause of breakdown will pro-
bably be due to excessive local heating at the weakest spot, and in such
a case a partial resonance producing a greater form factor is not serious
provided it does not increase the R.M.S. value. I say this with con-
siderable diffidence, and I'm afraid Mr. Duddell will not agree with me.
I only wish that Mr. Duddell had written a paper on this subject instead
of myself ; he has made a large number of experiments and has a fund
of information which ought lo be published for the benefit of the electri-
cal industry ; I hope he will, in communicating his remarks to the
Journal, expand them considerably and give us further details of his
careful study of this most important subject.

Major Cardew suggested that the assumptions made in the paper as
to the suddenness with which a circuit is made or broken are untenable.
He suggested that the switch itself had a certain variable amount of
capacity which was really in series with the capacity of the cable, and
on closing the switch this capacity was gradually reduced, thus gradually
raising the potential of the cable before the circuit is actually closed.
Now if we take the capacity of a "aD" cable, we find that it is about
equivalent to that of two plates 750 sq. ft. area, or 28 feet square,
separated by, say, i". What can the capacity of the metal parts of the
switch be in comparison with this ? Probably not more than -njJinjth
part until the contacts came within striking distance, then a spark
passes and the insulation of the air-gap being totally broken down, the
circuit may be said to be closed instantly. Again, on opening a circuit
Major Cardew suggested that the air arc which is formed and gradually
lengthened causes the current to gradually die down. Now experi-
ments show that this is very far from being the case. A high-tension
air arc seems to finally extinguish itself with what might almost be
termed explosive suddenness, even though it may have lasted several
seconds previously. Whatever be the reason it has now been estab-
lished beyond the region of doubt that the high-tension air arc is about
the most vicious phenomenon possible in setting up high potential
oscillations in the circuit. I admit that one would nalurally expect the
air arc to be equivalent to a gradual, and an arc under oil to an abrupt
opening of the circuit. Oscillograph experiments show just the reverse.
If a circuit be broken under oil there will be no high potential oscil-
lations called into existence. As Professor Carus- Wilson has pointed
out, this is of the greatest moment to engineers who have to deal with
Vol. 82. 62

792 CONSTABLE, FAWSSETT AND FIELD. [April 28rd,

Mr. Field, high-voltage machinery. The correctness of the above statements is
beyond dispute, having been Qstablished by numerous experiments both
in this country and in the States. It shows us at once that all apparatus
such as switches, fuses, etc., where an arc can possibly form in air most
be avoided in high-tension circuits, whereas oil switches and oil fuses
may be used not only with certainty but without engendering the danger
of high potential rises. I now wish to touch upon the matter of charging
gear for cable networks. A good deal of correspondence has taken
place in the electrical papers lately on this subject. It seems to have
been the experience of some stations in this country that a main-
charging gear is necessary. It is noteworthy that in the States I
did not come across a single instance where one was installed. However,
I would say, that if any engineer wishes one, let him have it by all
means, but let it take the form of an absolutely non-inductive resistance.
For this purpose a water resistance is manifestly correct. Anything in
the nature of self-inductions, transformers, and the like, should be
discarded as highly dangerous. Mr. Partridge has lately described an
arrangement used at Deptford consisting of a transformer, the high-
tension side of which is placed in series with the cable, and the low-
tension side gradually short-circuited through a water resistance. This
has apparently given satisfaction, and all I would say about it is, that
Deptford has been very fortunate. The t)rpe of gear is certainly risky,
at certain instants it introduces practically a pure self-induction in series
with the capacity. It would appear that the values are such that the
combination does not happen to be a dangerous one. We must
remember that the Deptford wave form is a very nearly true sine-wave
without ripples. If a number of different harmonics existed of any
appreciable amplitude, it is clear that with the possible variations of
capacity, self-induction, and slight variations of speed, resonance with
one or other of the harmonics would be very likely to occur before
long. Water resistance mains-charging gear can be made, in fact is
made, entirely reliable, simple in operation, comparatively inexpensive,
and by proper construction the insulation can be made as high as
necessary. It is in fact thoroughly practicable, both mechanically and
electrically.

With regard to applying high-voltage tests to cables, in my
opinion a mediumly severe test for a long period, say 30 minutes, is
preferable to a much higher voltage applied for only a few seconds.
If a cable will stand a test for 30 minutes, it is very unlikely that
it will be permanently damaged by the strain put upon it. If, how-
ever, a very high voltage be applied for five seconds, it is possible
permanent damage may be done without actually breaking down the
cable. It may stand for five seconds, but break down after ten. This
means that deterioration is going on at some spot in the cable during
those ten seconds, and consequently considerable deterioration (pro-
bably scorching as explained theretofore) may have already taken place
at some spots during the first five seconds.

Mr. Atchison's communicated remarks are of great interest. .1 pre-
sirnie the alternator used was a comparatively small one ; I should
judge somewhere in the neighbourhood of 5 kilowatts. Resonance

1903.] ELECTIONS. 793

with the fifth harmonic required 27 m.f . capacity — this bears out the Mr. Field
contention of the paper that under ordinary central station conditions
resonance with low harmonics are not likely to occur, but only with the
higher ones. I wish to thank Dr. Thornton and Professor Hay for the
references they have given to previous experimental work on the
subjects treated in this paper.

Mr. W. B. Hird's remarks have already been answered in this
reply. I wish further to thank Dr. Henderson for the table he has
worked out and appended, and lastly, to express my appreciation
of the generous manner in which my paper has been received and
discDssed both in Glasgow and London.

The President : Gentlemen, I ask you to accord a most hearty vote The
of thanks to the authors for their papers. I am sure they have been
most interesting in every way, while the discussion we h^ve had has
been particularly instructive, and really shows the value of the papers.
The vote was carried by acclamation.

The President reported that the scrutineers announced that the
following candidates had been duly elected : —

As Members.
Charles Orme Bastian. | Henry Sherman Loud.

As Associate Members.

President.

Joseph John Perkins Barker.
Hermann Bohle.
Frank William Davis.
John Walter Henry Hawes.
Alexander Percy MacAlister.

James Geo. McLean.
James Mitchell-Cocks.
Thomas Penrose.
Philip Sydney Saunderson.
John Vincent.

Josiah Mower Wallwin.

As Associates,
Edward Coveney. | John H. Pennefeather.

As Students,

Hubert Henry Andrews.
Isaac Henry Becker.
Randal Eugene Golden.

Frederick William Halford.
Richard Pentony.
Kenneth John Thomson.

794 TRANSFERS, DONATIONS TO LIBRARY, ETC. [April 30tti,

The Three Hundred and Ninety-third Ordinai7 General
Meeting of the Institution was held at the Institution of
Civil Engineers, Great George Street, Westminster, on
Thursday, April 30th, 1903— Mr. Robert K. Gray,
President, in the chair.

The Minutes of the Ordinary General Meeting held on April 23,
1903, were read and confirmed.

The names of new candidates for election into the Institution were
taken as read, and it was ordered that their names should be suspended
in the Library.

The following list of transfers was published as having been approved
by the Council : —

From the class of Associate Members to that of Members —

Randell Howard Fletcher. I Gerald Hart Jackson.
John H. C. Hewett. I Herbert William David Lewis.

Julius Leonard Fox Vogel.

From the class of Associates to that of Associate Members —

John Daniel Dyson. | William Fennell.

Francis William Hewitt.

From the class of Students to that of Associate Members —
Francis Powell Williams.

From the class of Students to that of Associates —
Arthur Blok.

Messrs. R. B. Hungerford and C. J. Phillips were appointed scruti-
neers of the ballot for the election of new members.

Donations to the Library were announced as having been received
from the Museo Civico, Como, and Mr. D. S. Munro ; and to the
Building Fund from Messrs. J. Grant and H. Owen, to whom the thanks
of the meeting were duly accorded.

The Chairman : With reference to these donations, I may mention
that the first is from the Museo Civico, of Como, who have sent for our
Library a copy of a volume, with an illuminated cover, connected with
what has been done by Volta. They also sent us eight copies for
distribution at our discretion amongst various Libraries, and to-day the
Council decided what should be done in distributing these. I mention
this gift specially because it comes from a rather important body, and
is a token of their regard for the members of the Institution who
recently visited Ital}'.

I have to announce that the annual conversazione will take place on
Tuesday, June 23rd, at the Natural History Museum, and that on June
nth a concert will be given. These dates have been selected because

1903.] AITKEN: DIVIDED A^ULTIPLE SWITCHBOARDS: 795

there will be in London in June the Delegates of the International
Telegraph Conference, and it was thought by your Council that it
would be proper to give these gentlemen an opportunity of being
present at the entertainments.

In front of me you will notice the shield which has been subscribed
for by our students, and which is destined to be placed on the tomb of
Volta at Camnago. I feel certain the members present will Hke to
examine it ; it is a work of art, and was designed for the students by
Mr. Gilbert Bayes, a former art student at the Finsbury Technical
College, a Gold Medalist of the Royal Academy School, and now
instructor in modelling at Finsbury. I may remind you that a replica
of this shield was deposited in the Volta Mausoleum, Camnago, by Mr.
Hewitt, who represented our students. When the shield is affixed to
Volta's tomb, the Museum of Como will be asked to receive the cast,
which is now at Camnago. Within the next few days the shield
will be forwarded to its destination.

The following paper was then read : —

DIVIDED MULTIPLE SWITCHBOARDS: AN EF-
FICIENT TELEPHONE SYSTEM FOR THE L^
WORLD'S CAPITALS.

By W. AiTKEN, Member.

The designing of an efficient telephone system for one of the great
centres of industry requires much careful consideration, as the subject
bristles with difficulties. The problem, however, is a most interesting
one. Any system proposed must be as simple as possible, consistent
with efficiency — quick, direct, reliable.

Before putting my suggestions before you it will be advisable
to consider briefly the methods that have already been put forward.

The general practice has been to divide the area to be telephoned
into sections, to place in each section an exchange, to connect the
various exchanges together by direct junction wires where the traffic is
considerable, and to connect the various exchanges or groups of
exchanges also to one or more junction centrals, through which
connections are obtained to small exchanges where the traffic is not
sufficient to warrant direct junctions being run, so that complete
intercommunication may be established. Figure i shows such an
arrangement.

The weak spot of such a system is the multiplicity of junction
calls. Only a small proportion of the total calls can be dealt with
direct by one operator. In the larger exchanges 50 per cent, of
the calls may be local, but in the majority of cases the percentage
will be much smaller, in some cases only 5 or 10 per cent. Fifty
to 95 per cent, of the calls have, therefore, to be handled by
two — in some cases three— operators. The service is not, therefore,
ideal. The call has to be passed from exchange to exchange, and a
junction call takes about twice as long to complete as a iQcal one,

796 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April 30th,

1908.]

AN EFFICIENT TELEPHONE SYSTEM.

797

The subscriber's number has to be received by more than one
operator. There is also the possibility of delay and inefficient trans-
mission because of the compHcations of the junction circuits and their
consequent liability to go out of order. In practice it is found that for an
efficient service where there are a considerable number of exchanges,
for every loo subscribers' lines twenty junction lines are required,
ID per cent, for incoming work and lo per cent, for outgoing work.
In addition the junction circuit is. much more complicated than a
subscriber's circuit ; its apparatus is more intricate and requires
more expert handling.

What is recognised as the best method of working junction lines,
and used by the National Telephone Company, is as follows : —
At the outgoing end the lines are multipled three times on every
two sections, so that every operator has every line almost directly
in front of her. At the incoming end the junctions are arranged
in groups of 25 (average number) per operator and end in plugs^ only

Fig. 2.

signalling apparatus being in addition. A service or order wire is
provided per 25 junctions. This at the outgoing end is multipled
on every operator's keyboard, and is connected to her telephone by
pressing a small push-button. At the incoming end this service wire
is connected direct to the operator's receiver. When a subscriber
calls, the first-mentioned operator connects with the service wire and
informs the listening operator at the other exchange the number
wanted, this operator allots the junction to be used as she knows by
the position of the plugs what lines are available, tests the line
wanted, and. if free, inserts the junction plug, the originating operator
at the same time connecting the subscriber to the junction specified.
The subscriber may be rung by cither the originating or the incoming
operator but, preferably, by the latter and automatically. When the
clearing signals are received from the subscribers by the originating
operator she withdraws the plugs and automatically signals to the
incoming end, the operator there then withdrawing the plug also.
The following is a description of two typical junction circuits : —

798 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April 30th,

Relay Ring-through functions worked by Call Wire,

Fig. 2 shows the connections of a call wire junction line between
two exchanges worked on the above system. This diagram should be
considered in connection with Fig. 14.

At the outgoing end A, a local or subscriber's cord circuit is shown,
L being the listening key, C the bridging coil, D the 250-ohm clearing
relay with lamp E in parallel, and joined up so as to retain when
pulled up by battery F.

A single tongued relay G is connected to the bush of the junction
jack. The insertion of a calling plug into this jack operates relay G,
and thus cuts the earth off the junction lines and bridging coil H.

The operator at the incoming end B obtains an engaged test
through the tip of the junction plug and one outer tongue of relay N,
on third conductor of the plug, through tertiary winding R of her
induction coil. If there is no click she then plugs in, thus operating
relay N, which disconnects the tip qf the plug from the tertiary winding
and connects it direct to the A line ; this relay also joins clearing relay
M (250 ohms resistance) from the centre point of retardation coil K,
direct to earthed battery P.

The jack into which the junction line is plugged is that shown in
Fig. 14. When the subscriber at the incoming end depresses his key,
the clearing relay D (Fig. 2) at the outgoing end is brought up and
retained, thus giving the clear at the outgoing end.

When the outgoing operator withdraws the calling plug from the
junction jack, the relay G is released and puts earth on the centre point
of the junction line, so that relay M is actuated and the clearing lamp
O glows.

When the incoming operator withdraws the plug from the jack,
the relay N is released and everything thus returned to the normal
condition.

Central Battery Junctions Worked by Call Wire.

Fig. 3 shows the call wire circuit and also the outgoing and
incoming ends of a junction. It will be noticed that at the outgoing
end no relays are required to join up or cut off the clearing current, as
this is already on the lines on the insertion of the plug q, (See Fig. 15.)
The bush or test connection of the jack has a 30 ohms resistance coil
joined in series to earth to complete the circuit for the supervising
lamp on the calling plug. The call wire is brought through a key so
connected that adjacent positions may be joined together, and terminates
on the operator's instrument. A self-restoring indicator relay is also
bridged on the line for night use, in the night bell contact of which is
joined a lamp, battery and relay for calling when the operator is not
listening, a special key being fitted to restore the indicator. In
this system also no listening or testing keys are used, these being
replaced by a relay C in the third conductor of the cord, and an
induction coil with three windings connected so that in the normal
position the tip of the plug is joined to the tertiary winding ready to

1903.]

AN EFFICIENT TELEPHONE SYSTEM.

799

receive the engaged click, and on the insertion of the plug the relay
is actuated and the tip is broken from the induction coil and connected
through to the line. This relay lis also in circuit with the clearing
lamp which is 12 volts and has resistances placed in series with it
In this circuit a ringing control is used. When the key is depressed

a clutch holds it in that position and connects up the ringing generator.
When the telephone is taken from its rest an excess of current actuates
the electromagnet and releases the clutch, thus cutting off the genera-
tor. The only other special point in this circuit is the method employed
for clearing, so that on the called subscriber replacing his telephone the
clearing signal may be given right back to the calling plug circuit at

800 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April 30th,

the originating exchange, and on this plug being withdrawn the clearing
lamp in the incoming junction plug circuit glows.

This is accomplished by means of a special relay G having two
windings, one of very high resistance (12,000 ohms), so that the supw-
vising relay on the calling plug at the originating end will not be
actuated through it. The other coil is of low resistance to hold up the
armature of the relay. This keeps the clearing lamp out by shunting
it with a 40-ohm coil. The high resistance coil of relay g is short-
circuited by the armature of the supervisory relay D in order that the
line resistance may be reduced to a minimum, so that the supervisory
relay on the calling plug at the outgoing end may be actuated and

TEST BOARD

MULTIIM.E SWITCHBOARD

'-•OU COMItKTHM

KWlTmi J*C«

RELAY BOARD

INTERMEDIATE

DISTRIBUTING

BOARD

CALUNG LAMP A LOCAL JACK

^ CENTRAL BATTERY

' (M VOLTI)

•HiliiilHililh-

Fig. 4.

so keep the clearing lamp on that plug out while the junction is
engaged.

It will thus be seen that when the local subscriber on the incoming
junction has finished his conversation and replaces his receiver on the
rest, the circuit is broken and the armature of the supervisory relay D
falls back, and the high resistance coil of relay G is placed in circuit in
the line. This releases the supervisory relay on the calling plug at the
originating end and causes the corresponding lamp to glow. The high
resistance coil of relay G is, however, during this time still keeping its
armature attracted, but on the withdrawal of the calling plug at the
outgoing end this is released as the current is cut off, and the lamp
glows, giving the signal to clear.

The condenser placed in the line side of the repeating coil is used

1903.]

AN EFFICIENT TELEPHONE SYSTEM.

TOl

to improve the talking, othenw^ise the choking effect of relay G would
make speech impracticable.

We will just glance for a moment at the circuits of an up-to-date
Exchange — on the Common Battery System — so that you may appre-
ciate the slight additional complications which are made necessary
by the divided system to be described. Fig. 4 shows the line circuit
of the Western Electric Company's system. Fig. 5 shows the line and
cut off relays in detail.

In such a system all lines are multipled on every section of switch-
board, each containing about 300 subscribers' lines served by three
operators. The multiple and answering jacks are branched from opposite
sides of the intermediate distributing board. A line and cut off relay is
in combination with each line. The subscriber's instrument has a con-

Plan of tower (Cut-off) Relay
Fig. 5.

denser in circuit with the bell normally, which prevents the central
battery discharging. When a call is made by taking the telephone
from its rest, a path is provided for the current through the microphone
and induction coil, and the line relay is energised. The calling lamp in
the local circuit glows, and the operator answers by inserting a plug
into the jack hole immediately above the lamp. The cut off relay is
then energised and cuts the line relay out of circuit so that the calling
lamp ceases to glow. The connection is completed by the insertion
of the other plug of the same cord into the multiple jack of the line
wanted. A skeleton cord circuit is shown in Fig. 15.

The line and cord circuit of the Kellogg Switchboard and Supply
Company are shown in Frgs. 6 and 7. The peculiarity of this line
circuit is that there are only two wires throughout the switchboard
per line instead of three as is usual, and that the lines are not connected
to the multiple until the plug is inserted. The cut off relay coil is
tapped off the line circuit instead of being on the third wire. The

80^ \1TKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April 30th,

Note.— The blocks of Figs. 4, 5, 6, 7, 8, were kindly lent by the Electrician.

1903.]

AN EFFICIENT TELEPHONE SYSTEM.

^08

cut off relay is shown in detail on
Fig. 8.

Having now considered the
general principles of the usual
methods of working, let us consider
a concrete case, dealing with an area
served by two large exchanges.

Such a condition could hardly
exist in practice. There would
almost certainly be lines to smaller
and more distant exchanges. In
large systems it is usual to reckon
the number of junctions necessary
at 2o per cent, of the number of
subscribers' lines in an exchange.

In considering the following
hypothetical case, I have calcu-
lated on 15 per cent, being neces-
sary for working between two
large exchanges.

Between two exchanges of
10,000 lines each 15 per cent, of
junction lines would be required,
7i for incoming work to one ex-
change and 7i to the other, or
1,500 metallic circuit lines. To
accommodate the incoming junc-
tions 20 switchboards (10 in each
exchange) would be necessary
with 25 lines per operator and
three operators* positions per
board. Sixty operators and six
supervisors are, therefore, required
to work the incoming junction
lines in the two exchanges, and
as each subscriber's operator has
a large proportion of connections
for the other exchange she cannot
attend to so many calls as she could
do if all the work were local. On
each junction switchboard the
complete multiple of 10,000 sub-
scribers' lines must be repeated,
and on every subscriber's section
1,125 spring jacks must be multi-
pled for outgoing work to the
other exchange, these being multi-
pled three times on two sections
to place them well within the
reach of the operators.

a&4 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April SOlh,

The provision of junctions between exchanges is a difficult one, for
to provide an ideal service the number of circuits must be sufficient to
carry the maximum number of calls at the busiest half-hour of the
busiest day, and necessarily many of these junction circuits would be
lying idle the greater part of the time.

In the earlier days of telephony there was not much need for the
divided board, as the great cities were effidently telephoned with
switchboards having a capacity of from 6,000 to 15,000 lines. When
necessary a number of these were fitted and connected by junction
lines. Even to-day the system I advocate is worthy of consideration
practically only in the world's capitals, where it may be expected that
the number of telephone subscribers may reacli something like 100,000.

Underground work is essential with the divided board, owing to

Fig. 8.

earths, etc., giving false calls, and it is only of late years that facilities
could be obtained for work of such a nature, and even to-day way-
leave facilities arc not always obtainable.

It is only in recent years also that satisfactory conduits for large
capacities have been introduced, and that hermetically sealed lead-
covered air-space paper cables containing a large number of con-
ductors were manufactured. The system I am about to describe to you
is just beyond the experimental stage, and I think the time is now ripe
for it to receive careful attention.

Such a system must, of necessity, be an undergrourfd metallic
circuit system. The average length of subscribers' lines would be
greater with a divided system than with the junction system, as a
larger area would be served from a central, but against this must be
placed the great reduction in the number of long junction circuits with
their elaborate switchboard equipment.

In my opinion, it is only by adopting a divided multiple switchboard
system of working, in which the exchange is divided into several
sections, the subscriber having the power to call any one of the sections
at will, the large cities of the world may be more efficiently telephoned.

1903.]

AN EFFICIENT TELEPHONE SYSTEM.

805

806 AITKEN DIVIDED MULTIPLE SWITCHBOARDS : [April 30th,

By a divided multiple exchange, I mean an exchange divided into
two or more groups, each group having a multiple of a proportion only
of the total subscribers' lines, each subscriber having the power of calling
each of the groups at will and obtaining connection with the subscribers
multipled thereon without the intervention of a second operator. The
advocates of the divided multiple board system believe in centralisation
and the abolition of junction lines as far as possible. The multiple of
each switchboard or division is made as large as can be convenientiy
reached by the operator, and where those who favour the divided
system differ from the advocates of the junction system is in that they
ask the co-operation of the subscriber by giving him the selecting of
the group of switchboards on which the line wanted is connected.
Two or three push-buttons or switches are fitted in combination with
the ordinary subscriber's instrument, one, say, labelled i to 10,000, the
second 10,001 to 20,000, and the third 20,001 to 30,000, or in other
suitable divisions. In addition to taking the telephone from the switch-

FiG. 10.

hook the subscriber has to press the button of the group in which is the
number required ; he then gets the connection direct instead of as in
the junction system, the first operator having to ask the second to assist
her in completing the connection in a large proportion of the calls.

The central exchange on a divided system consists really of two or
more great multiple switchboards serving a large area, and its total
capacity may be from 30,000 to 60,000 lines, according to the size of
the units and number of divisions. Instead, however, of having
junction lines between the exchanges the subscriber's line is branched
to each division and has a calling signal and answering jack on each,
so that it can be connected to each of the multiples of the several
divisions, his own line being multipled on one of the divisions so that
other lines may be connected to it. The subscriber can, therefore,
greatly expedite the rate of operating for a great proportion of his calls,
and at the same time he enables the operator to perform more work as
a second operator more rarely intervenes.

A proportion of junction working will still exist to the exchanges
more distant from the centre, but in most instances it will be possible

1903.]

AN EFFICIENT TELEPHONE SYSTEM.

807

to so design a system that 75 per cent, of the possible junction working
will be eliminated. I have, therefore, based my estimates on this
figure.

Fig. I shows a large populous area telephoned on the junction

i i "^

'i^

L.^

system, the total number of subscribers being 115,000 in thirty-seven
exchanges. The largest exchange has a capacity for 15,000 lines, or
13 per cent, of the total. In the two*largest exchanges there is 22 per
cent, and in three 26 per cent. Even if the three exchanges were each
of 15,000 lines they would only contain 39 per cent, of the whole.
Vol. 32. 63

808 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April 30th,

Fig. 9 shows the same area telephoned on the divided multiple
system for the same number of lines in fifteen exchanges. The largest
exchange has 45,000 lines and the next 30,000 lines. In the former
there is 39 per cent., in the two 65 per cent., and in three 83 per cent.
of the total.

The lines on the diagrams indicate direction only and not the
number of circuits necessary.

I may be accused, with a good deal of justice, of comparing a

Fig. 12

theoretically good divided system (Fig. 9) with an imperfect junction
system (Fig. i), but with the latter system local conditions and limita-
tions, such as rivers, public parks, low-class residential neighbourhood,
etc., form natural boundaries beyond which for the sake of economical
working it is not desirable to extend, and therefore single exchanges of
the maximum size are not always possible or essential, whereas this
does not apply to the same exteift to the former.

Milo G. Kellogg, of Chicago, was, I believe, the first to design and
advocate a divided multiple board ystem, and a number of exchanges

1908.]

AN EFFICIENT TELEPHONE SYSTEM.

809

are now working in America on this plan. Usually two divisions
have been adopted, but in one or more cases a four division board has
been installed. In these pioneer exchanges the system was complicated
by polarised relays and indicators on the switchboards, and at the
subscribers' offices by commutated magneto generators.

In at least one case the magneto generators were replaced by the
primary speaking battery, acting through an induction coil, giving a
" kick " when the circuit was made and broken, sufficient to energise
the calling signal (see Fig. lo). Suitable switches connected the current
generating apparatus to line in the proper direction to actuate the
signalling apparatus in the division required.

In one circuit a positive and a negative polarised indicator are in
series across the loop and two^imilar indicators in series are connected
as a tap to earth on one wire of the metallic circuit. (See Fig. ii.)

Fig. 13.

In another case a positive and a negative polarised indicator are in
series and tapped to earth, two o£E each line. (See Fig. 12.) Four-division
exchanges are thus obtained.

With the development of the central or common battery system of
telephone exchange working and the popularising of the telephone the
need for a simpler way of working great central exchanges became
more urgent, and when considering this question I was struck with the
idea of working a divided system from a central battery. I had
previously designed two circuits which led naturally up to this, one
in February, 1898, with a retaining electromagnet at the subscribers'
instrument, which allowed a momentary depression of a key (thereby
mechanically completing the circuit of the central battery through the
calling relay to earth) to give a permanent signal to the operator (Fig. 13)
and another in June, 1899, in which I removed the electromagnet from
the subscribers' instrument and provided a local retaining circuit on the
relay at the exchange, utilising the ordinary line relay coil for this
purpose (Fig. 14).

The latter I preferred to use for my divided board system, as it
simplified the apparatus at the substation.

In this system non-polarised relays are used, energised from a
central battery when any one of the simple switches at the substation

810 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April 30tll,

RING THROUGH SYSTEM

jm\

D ^

Imt — I

h/wv

— nnnnp —

lUtt

mmT

€> ^

j^^^jK-jvfm

^fT

I — **""/T

Fig. 14.

1903]

AN EFFICIENT TELEPHONE SYSTEM.

811

instrument is depressed. The caller can thus select any one of two or
three groups of multiple switchboards required.

A greater number of combinations could, no doubt, be obtained
by step by step movements, but at the expense of simplicity.

In a two-division exchange having two groups of multiple switch-
boards, two simple single make-and-break relays are necessary ^ the
central and two earthing or grounding switches at the substation.

In a three-division exchange two double (or one triple and one
double) make-and-break relays are used in connection with the two
wires of the metallic circuit, and in connection with them are three
calling lamps, one on each of three groups of multiple switchboards.

fQ<

^^' i^

r^'=

Tap

Fig. 15.

L^D.-

Any of the well-known forms of instruments may be used in conjunc-
tion with these systems, it being only necessary to fit in combination
therewith a simple two- or three-way switch as required, one position
earthing the A line, another earthing the B line, and the third earthing
the A and B lines simultaneously (the latter in the three-division only).
The switch-lever or plunger is put momentarily in one of these posi-
tions to give a permanent signal to the attendant at the corresponding
switchboard.

With a two-division system, shown in skeleton on Fig. 15 and the
line-circuit in more detail on Fig. 16, two switchboards, A% B'(Fig. 15),

819 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April 30th,

of suitable size are provided, and one-half the total capacity is multipled
on one line of boards and half on the other. Each subscriber's instru-
ment has two push-buttons, A', B', one for earthing the A and the other
for earthing the B line.

Each line, after passing through the usual test-board or main
distributing frame. T.B. (Fig. i6), is connected to a special double
intermediate distributing frame, I.D.B. To a central set of soldering
tabs the two test-board wires are connected, and from the same set a
triple wire per circuit is carried to the multiple jacks, M.J., of one line
of boards. From a parallel strip of tabs on one side of the central line
tabs a quadruple wire per circuit is carried to the answering jack, A. J.*,
and calling lamp, C.L.', on the same line of boards and from a parallel
line of tabs on the other side of the central line tabs another quadruple
wire per circuit is carried to an answering jack, A.].', and calling lamp,
C.L.», on the second hne of board. A quad-cross-connecting wire
connects the central line tabs and the tabs on both sides. All wires
from the intermediate frames are made up in cables, but the wires
between tabs are made in loose quads to allow of ready alteration with
the object of changing the local position of any subscriber so as to
equalise the work per operator, as in this arrangement it is necessary
to allow distribution on each line of boards. Each quad is made up of
the two hne wires, the test wire and a lamp wire. The test wire also has
a connection through the cut-off relay coil to earth. Each line wire has
a connection through a tongue and contact of the cut-off relay, C.O.R.,
and its line relay coil, L.R.' or L.R.«, to battery and earth. E^h
tongue of the cut-off relay, C.O.R., has also a connection to the tongue
of the line relay associated with it, the under-contact of each hne relay
being connected to earth.

The answering jacks and calling lamps are arranged in the usual
way, with pilot relay, P.R, and lamp, P.L., night-bell, N.B., etc., as
shown at Fig. i6. The calling lamp has also a connection to the line
side of the relay coil, so tl^at it is in parallel with that coil. The action
is as follows : —

When a subscriber depresses key A' (Fig. 15) there 'is a circuit
from the earthed central battery through line coil of relay, k (with
lamp, j, in parallel) associated with that Hne, through one contact
and tongue of cut-off relay, h, through the A wire to earth at key A'.
The line relay, k, is therefore energised and the lamp, j, glows. There
is then a local circuit from earthed central battery through line coil, k,
and lamp, j, in parallel, through contact and tongue of cut-off relay, h,
through tongue and contact of line relay, k, to earth, and the lamp,
therefore, continues to glow after the key A' is released until the
operator answers. This is done by inserting a plug, q, of a connection
set into the answering jack, C*. Another local circuit is then estab-
lished from earthed central battery, i, through the shunted lamp, p, on
the third conductor of the cord to sleeve of plug, q, bush of jack,*C,
over test wire, through cut-off relay coil, h, to earth. The cut-off relay,
h, is, therefore, energised and the hne relay circuit broken by the
tongue leaving the outer contact, so that the caUing lamp ceases to
glow. The subscriber may then be connected with any other on that

X903.]

AN EFFICIENT TELEPHONE SYSTEM.

813

TB.

PL'

P.R?

-4iflri-u-,

a.j!,

f —

j> ,

!lr!
I*. I

IfRC

PR'-

-K'

s [

llllllllll^

N.B

_ysAM-

Fiti. i6.

814 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April 30th,

multiple. Should the B» key be depressed, the other line relay and
lamp will be energised, the retaining circuit be broken by the cut-off
relay being energised by a connecting set used by an operator at the
second line of boards, and a connection completed thereon.

Each operator may have 300 answering jacks and calling lamps
under her control, but will only attend to half the total number of calls
from each subscriber.

As there are fewer junction lines between exchanges on the divided
system, the outgoing junction work will be less and each local operator
will therefore be able to attend to a greater number of lines.

Presumably on the junction system about 50 per cent, of the calls
would be for the second exchange, and as a junction call takes twice as
long to complete as a local one, if most of the work is made local, as oa
the divided system, the operator will be able to attend to approximately
50 per cent, more lines, so that instead of 66'/3 subscribers* sections
being necessary on the junction system at 100 lines per operator,
only 44V3 sections would be necessary on the divided system.

There will also be a very considerable saving in floor space, and
consequently rent or value of premises, as the length of the unnecessary
junction and subscribers' sections would be about 270 lineal feet, made
up of 20 junction sections and 22 subscribers' sections, each about
6 ft. 6 in. long.

If three 10,000 line exchanges were opened on the junction S3rstemthen
possibly treble the number of junction lines, multiple junction sections,
and operators would be necessary, as 1,500 lines are required between
A and B, 1,500 between B and C, and 1,500 between A and C, and the
subscribers' (or local) operators can each attend to a still smaller
number of calls, because a still greater proportion of their work is over
junction lines, and each local operator would then be able to attend to
a smaller number of lines, say 90 instead of 100. The number of
switchboards and number of operators would therefore be increased,
while there would be no increase on the three-division system.

With a three-division system, shown in skeleton on Fig. 17 and in
detail on Fig. 18, at the central exchange three independent multiple
switchboards are fitted, one-third of the total number of lines being
multipled on each. Each subscriber's line is multipled on one of the three,
but has an answering jack and calling lamp (or other indicator) on each.
An operator may therefore have 450 calling lamps and answering jacks
to attend to— 150 in connection with the lines multipled on that group
of switchboards and 150 each in connection with the other two groups,
so that the subscribers can call and be connected to the other lines
that are multipled thereon. Three relays, as before, are required for
each circuit, one — the cut-off relay, C.O.R. (Fig. 18) — having two
springs which are made to break from two contacts, as before, by the
action of the armature when the relay is energised. The coil has one
side connected to the earthed side of the central battery and the other
side connected to the test circuit of the spring jacks, as is usual. The
two line relays differ from those of the two-division board and more
nearly resemble the cut-off relay. One has two springs which break
from one and make on two contacts when energised, the other has

1908.J

AN EFFICIENT TELEPHONE SYSTEM.

815

three springs which break from one and make on two contacts when
energised. This modification from Fig. 17 was necessary to get a
common circuit from pilot relay, P.R.3.

The coil of each line relay, L.R., has one side connected to the
earthed central battery, the other side being connected to the outer
contacts of the cut-off relay, C.O.R. The relay tongues or moving
springs of the cut-off relay are connected one to each line, each also
having parallel extensions to one of the tongues of its respective line
relay ; these tongues, when the relays are energised, make contact with
inner points connected to the earthed side of the central battery. A
small incandescent lamp, C.L.', connected with the No. i, or A, group
of boards is in parallel with the coil of one-line relay, L.R.», and a
second lamp, C.L.', in connection with the No. 2, or B, group of boards,
in parallel with the coil of the other line relay, L.R.*. The line relays

Fig. 17.

have another tongue, which rests normally against an outer contact,
but when actuated by the armature when the relay is energised breaks
from this point and makes contact with another. Normally the circuit
of the A and B lamps are completed through these contacts. When,
however, the relay L.R.' immediately associated with the A group of
boards is energised the circuit of the B lamp C.L.' is cut ; similarly,
when the B relay L.R.* is energised the A lamp C.L.' circuit is cut and
if, therefore, both relays be energised at the same time the circuits of
both lamps will be cut. The circuit of the lamp C.L.3 in connection
with the No. 3, or C, group of boards is then established, the circuit
then being from the earthed central battery through pilot relay, P.R.3,
through the tongue and inner contact of the line relay, L.R.', through
I.D.B., through the C lamp to the inner contact and tongue of the line

816 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April 30th,

relay, L.R.», through the right-hand outer contact and tongue of the
cut-off relay, C.O.R., and the other tongue and under-contact of the
line relay L.R' to earthed side of battery.

Samples of suitable relays are on the table. With modern improve-
ments the dread of double and triple contact relays has disappeared.

At the substation three push-buttons are fitted (Fig. 17), and,
according to the number required, the subscriber presses the A', B%
or O key. When the A* or B» key is depressed the A or B calling
lamp glows, as described for the two-division arrangement, and when
the C key is depressed both lines are earthed and both line relays are
energised, the circuit of the A and B line lamps is cut and the lamp
associated with the third, or C, group of boards glows. When an
answering plug is inserted the cut-off relay is energised and the local
retaining circuits are broken and the C lamp ceases to glow.

The foregoing arrangement can be used practically with any cord
circuit. The following are a few examples. In the ring-through cord
circuit (Fig. 2) the cord is bridged by a suitable differential retardation
coil C, having its centre point connected through the coils of a relay
D, to the earthed central battery, a lamp E being in parallel with this
coil. The side of the relay coil farthest from the battery should be
connected to the contact of the relay, the tongue connected through a
spring and contact of the listening key L to earth, so arranged that
the relay circuit may be broken in the listening position. When a
connection is made and any one of the plungers at the substation is
depressed momentarily the armature of the relay is attracted and a
local circuit established which retains the armature, and therefore the
clearing lamp glows until the operator brings the key to the listening
position or withdraws the plug.

This arrangement may be used in conjunction with the ring-through,
system, in which one subscriber rings the bell of the subscriber wanted
or the operator may do the ringing. In the former case a generator is
supplied with each instrument, in the latter case this is not necessary.

In the ring-through system with relay and lamp which was designed
to replace the now practically obsolete call-wire system I preferably
use a cord circuit without listening key as shown on Fig. 14.

The operator's telephone is normally in circuit through the back
contacts of a triple relay in the third conductor of the cailing cord.
The operator is therefore ready to answer immediately she inserts the
answering plug, but when the connection is completed by the insertion
of the second plug her telephone is automatically cut out, as a local
circuit is completed from earthed battery, through coil of triple relay,
through sleeve of plug, bush of • jack, over-test wire, through coil of
cut-off relay to earth.

This combination, it is believed, will form the simplest manually
operated switchboard known. The operating is as follows : —

(a) When the lamp glows operator inserts answering plug.

(b) Tests line wanted, and if free inserts plug into jack of line

wanted.

1908.]

AN EFFICIENT TELEPHONE SYSTEM.

817

.TB

-^^0 1 ii_L...L.i.

thttt

trr.-j'

.^1

Fig. i8.

818 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April 30th,

Such a system, up to the present, has only been proposed with
central battery signalling, a primary battery at the subscriber's being
used for speaking.

The divided board system will work also most efficiently with the
Western Electric Company's common battery cord circuit when auto-
matic clearing on two lamps and speaking from central battery are
obtained. (Fig. 15.)

With the circuits of the Kellogg Switchboard and Supply Co., Fig. 7
it will also work excellently ; in fact, this company have specially laid
themselves out for building large exchanges on this system. Their circuits
have only two wires in the multiple and two-way plugs, and they have,
therefore, been able to reduce the size of their standard spring jacks to
three-tenths of an inch face measurement instead of the f in. as is
usual, and I believe they are now manufacturing switchboards of
20,000 capacity per division.

I would propose forming one huge central exchange of from
30,000 to 60,000 lines in the heart of each great city, this exchange
serving an area of about 14 square miles ; this, of course, would vary
with the density of the population, and the prospective number of
renters. With an underground system, and cables containing from
250 to 300 pairs each, such an arrangement is perfectly feasible. Four
main conduits should radiate from the central building, each containing
from 50 to 80 ducts, these branching out, as required, up to a distance
of from 2 to 2|^ miles from the exchange. Outside this area, say at 2i
miles' distance from the central, subsidiary exchanges should be formed.
•When these exchanges are of considerable size they would have direct
junction lines to the central, and incoming junction sections on each of
the three multiples of the central exchange ; where, however, the
junction lines were few the operator would call the multiple required
at the central by pressing the corresponding key in the same way as a
subscriber.

The outgoing junctions for these subsidiary exchanges would only
be multipled over one group of boards at the central, say the C group,
so that subscribers would call, say, numbers i to 16,000 by depressing
the A key, 16,001 to 32,000 by depressing the B key, and 32,001 to
45,000 and all subsidiary exchanges by depressing the C key. These
numbers of lines can perfectly well be placed within the reach of the
operators by using for the A and B multiples 6 feet 3 inch frames
having 9 panels of strips of 20 spring jacks measuring 8^^ inches by
i inch. Eighteen blocks of 100 jacks give a height of about 2 feet
9J inches. The answering jacks and calling lamps and number pegs,
in strips of 20, with space sufficient for 533 lines per operator (this
being about equal to 177 lines on a simple multiple, as each operator
only attends to one-third of the total number of subscribers' calls on a
three-division system) would occupy a height of about iij inches, so
that the height of the upper row of spring jacks above the keyboard
would be about 3 feet 9 inches.

The C line of boards could cither be made to accommodate a
slightly smaller number of subscribers' lines, so as to leave room for
the outgoing junctions, or the section could be still further increased in
^,ngth.

1D03.] AN EFFICIENT TELEPHONE SYSTEM. 819

For a 45>ooo line three-division exchange, reckoning that each
operator can attend to an average of 150 lines per multiple board, or a
total of 450 lines, the A and B groups would each consist of 107
multiple sections ; while reckoning that each operator at the C group
could attend to 100 lines only owing to the amount of junction work,
130 sections would be necessary.

E^ch group of switchboards (and possibly also separate intermediate
and main distributing frames) should preferably be in a separate fire-
proof room in practically separate buildings, so that in case of fire the
fireproof doors between could be closed and so confine the breakdown
to one group.

The premises should, therefore, consist of one central building with
flanking wings. In the basement of the central building one main
distributing frame should be fitted, arranged radially in four sections
of 12,000 or 15,000 in the shape of a Greek cross, the four conduits
opening out at the ends. On the ground floor should be similarly
arranged the intermediate distributing board and relay racks, the
former having two or three distributing fields, as it may be necessary
for equalising purposes to cross-connect the lines on one group of
boards and not on the other. In the central building might be the C
switch room, the A and B switch rooms being in the right and left
wings respectively. Preferably the groups or divisions of the exchange
should grow uniformly, as will be made clear by the following example.
If it is desired to convert a 9,000-line ordinary exchange into a two-
division exchange, and it is necessary to begin the second group with a
capacity of 2,000 lines, then whilst it is only necessary to provide 2,000
extensions of answering jacks and lamps on the 9,000-line frame, for
which there is plenty of room, the 9,000 lines require lamps and jack
extensions on the sections built for 2,000, and each operator would have
an abnormal number of lamps and jacks from the first line in front of
her, and these would require to be redistributed when further extensions
were made.

I think it must be granted, from what I have said that, from an
operating point of view a great boon would be obtained. by the introduc-
tion of the Divided Multiple Board System. Also that the made-up or
speaking circuits would be much simpler.

^ far as I can see the principal objection that can be urged against
It is that the system depends for its efficient working upon the co-
operation of the subscribers. We have been told that "men are
mostly fools." Must this be taken literally ? I think at any rate, not
sufficiently fools to spoil a divided system by wilfully or carelessly
calling on the wrong group or division of the exchange.

820 AITKEN.: DIVIDED MULTIPLE SWITCHBOARDS : [Apri!

COMPARATIVE ESTIMATE OF EQUIPMENT NECESSARY
FOR TWO IS.OOO-LINE EXCHANGES CONNECTED BY
JUNCTIONS AND ONE 3o,ooo.LINE TWO-DIVISION
EXCHANGE.

Apparatus for two

Apparatus for a

iSooo-Une

Description of the Apparatus.

30,000-linc

Exchanges.

Exchange.

Incoming junction sections (at 7^ %)

None

100

Subscribers' sections

66}

1,950,000

Multiple spring jacks

63 wire cable (30 yds. I.D.B.)

1,000,000

337,500 y<is.

195,000
None

168,750

Outgoing junction jack3

40,500 yds.

33 wire cable

,»

30,000

Answering jacks

60,000

30,000

Calling lamps

60,000

. 30,000

Double cut-ofF relays

30,000

Line relays

60,000

175,500 yds.

L . . (

198,000

(1,500 lengths
at 117 yds.)

V84 wire cable <

(3,000 lengths

J (

X 66 yds.)

2,250

M.C. junctions x lengfh X

None

2,250

Repeater coils for junctions

„

2,250

Condensers for junctions

2,250

Relays (12,000 ohm + 20 ohm) ...

2,250

Relays (local clearing)

Relays (on third conductors)

2,250

Clearing lamps

2,250

40-ohm resistance coils

2,250

30-ohm resistance coils

C Call wires between Exchanges with )
( equipment )

Lines of tabs on I.D.B

Cross connecting wire per line ...

Twin switches on instruments ...

30,000

390

Operators

200

Supervisors

845 ^t.

Length of switchboard

(Practically the two-division
equipment can be fitted in a
building necessary for one of
the 15,000-line Exchanges, and
therefore there would be a great
saving in cost or rent of buildings.)

433 ft. 4 in.

Increased length of lines

X X 15,000 1

(If the 2,340 junctions and call-

wires were each two miles long.

this would be equal to an average

increase in the length of each

of the additional 15,000 lines of

550 yards.)

Mileage of wire saved in the two- )
division Exchange )

5,707

(This used outside would increase

the average as above to about
880 yards^

Value of service

100

Power Plant with maintenance ...
(Great economy will be effected
by using one large Power Plant
instead of two smaller ones.)

Power Board Staff

Engineers-in-charge

1903.] AN EFFICIENT TELEPHONE SYSTEM. 821

TABLE OF CONTENTS.

PAGE

Cable work essential for Divided System 804

Cord circuit for Ring-through System 816

Cord Circuit C. B. System, W. E. Co's 818

KeUogg 818

Description of Single Multiple Exchange 801

Description of two Division Exchange 811

Description of three Division Exchange 814

Distributing Board (Intermediate) 812

Divided Multiple Boards, Area served by 806, 818

„ „ „ Allocation of lines to operators 814

„ „ „ Cable work essential 804

„ „ „ Central Battery 809

„ „ „ Centralisation 806

„ „ „ Definition of 806

„ „ „ Essential for World's Capitals 805

„ „ „ Inventor of 808

„ „ „ Incoming Junctions 818

„ „ „ Indicators with 809

„ „ „ Line circuit 811

„ „ ,, Outgoing Junctions 818

„ „ „ Possible size of • 806

„ „ „ Subscriber's Lines, Length of 806

„ „ „ Subscriber's office equipment ... 811,816

„ „ „ Subscriber's operating 816

„ „ „ Suitable buildings for 819

Divisions should grow uniformly 819

Junction Calls, Slow down service 795, 814

Junction Calls, Repetition of numbers 795

Junction Lines, Apparatus 797

Junction Lines, In relation to Switchboards and Operators ... 803

„ Increased cost of equipment 797

„" (Incoming) on Divided System 818

„ Operating on Divided System 806

„ Outgoing and Incoming 796

„ (Outgoing) on Divided System 818

,. Proportion of, to Subscriber's Lines 796

„ Provision of 804

„ Reduction of by Divided System 807

KcUogg, Milo G 808

Kellogg Switchboard and Supply Co. 's System 80 1

Manually Operated System, Simplest 816

Relays for Straight C. B. Board 801

„ „ Two Division Board 811

„ „ Three Division Board 811, 814

Ring-through System, E. M., on subscriber's instrument 809

822 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April SOlh,

PAGE

8ii

796

Telephoning an Area, Usual method 795> S08

Ring-through System, Earthing Key ...
Junction circuit

Divided Board Method

Western Electric Go's C. B. junction circuit

„ „ M System

References.

Patent No. 4699, March 25, 1890. M. G. Kellogg.
Patent No. 5,928, March 30, 1900. W. Aitken.
Patent No. 10,124, June i, 1900. J. E. Kingsbury.
Patent No. 18,031, October 18, 1900. Milo G. Kellogg.

808

798
801

Mr.

Laws Webb.

Mr. Herbert Laws Webb : I have read Mr. Aitken's paper with a
great deal of interest. The telephoning of very large cities is a subject
which, of course, telephone engineers look at as a daily increasing
problem. I am quite sure that all telephone men must admire the
ingenious manner in which Mr. Aitken has worked out the circuits erf
the divided multiple system to adapt them to common battery working.
However, on the broad lines of the problem my opinion is that it is
working in the wrong direction to advocate divided multiple exchanges.
In the first place, such a system largely increases the line plant. It
must necessarily greatly increase your average length of subscribers'
line if you divide your city up into very large districts, and I think it
will be found in all large telephone systems that the line plant repre-
sents by far the greater proportion of the cost of the whole plant. I
think even where line costs are the cheapest the percentage of cost of
the liAe plant is about 60 per cent, of the cost of the whole system, and
to save in the exchange plant, which is the smaller item of cost, and
increase in the line plant, seems to me to be working in the wrong
direction as far as cost is concerned. I think in very large cities, where
it is well known that the expense of building underground lines is much
greater than in smaller places, that would bar out the divided multiple
board altogether on the question of capital cost. The other point that
seems to me to be very largely inadvisable with this system is that it
puts back the operating of the service into the hands of the subscriber.
W^ith the common battery we have practically taken the operation of
the service entirely out of the hands of the subscriber. The subscriber
has the simplest action to perform ; lifting the telephone off the support,
which he must do in order to use it, automatically gives the calling
signal, and in replacing the telephone, which I suppose 999 out of 1,000
do properly, he automatically gives the signal to disconnect That
gives us undoubtedly the cleanest, the quickest, and the simplest service
that it is possible to give. In all systems where part of the operating
is done by the subscriber there are numerous troubles due to the sub-
scrit)er's lack of proper care in operating. If you put these two or
three buttons on every instrument for the subscriber to press according

19(».] AN EFFICIENT TELEPHONE SYSTEM : DISCUSSION. 823

to whether he wants one number or another, in very many cases he will Mr.
press the wrong button and get the wrong operator. Then you may
expect something like this to happen : the subscriber gives the number
that he wants, and the operator says, " You have pressed the wrong
button." He says, ** What ? " Then the operator gets a little more
impatient, and says rather shortly, " You-have-pressed-the- wrong-
butt on ! " And the subscriber sa)rs, " Hang your buttons ! Why
can't you give me my number?" In a great many cases that
is bound to be what would happen, more or less. The language
in some cases would be worse, and in other cases it would be
better. Consider, for instance, one of Mr. Aitken's proposed world's
capitals systems of 115,000 subscribers. You would have an average
daily traffic there, at flat rates, of well over one million calls. All of
those million calls would not come from expert subscribers. It is not
always the man who signs the contract who uses the telephone ; it is
used by all sorts of people, from the office boy down — or up, according
to which •way you look at it— and it is used very largely by strangers.
Every world's capital always has a large floating population, and if you
have 115,000 telephone stations you would have a large number of
public stations, so that a large proportion of your daily traffic would
be from people who are not expert in using that particular system.
Therefore a pretty fair percentage of your million calls a day would be
calls that would be sent in wrongly. That would give trouble ; that
would need extra attention, unprofitable work on the part of the
operators and the supervisors and the rest of the exchange staff. I
do not think that you can plan out any telephone system nowadays —
we have learnt something of late years of the telephone-using public —
without keeping a very careful eye on the public and on what it does
with the telephone at the public end of the system.

There are one or two points that occur to me in Mr. Aitken's
estimates of operating values. I noted somewhere that he reckons a
junction call as being the equivalent in time of two local calls. That
seems to me quite excessive — that it should take twice as long to operate
a junction call as a local call completed at the same switchboard. The
experience in New York, which for the past eighteen months or so has
had uniform common battery working, is that the difference in time
between completing a local call and a junction call is nothing like so
much as that. The very careful tests made of a large number of
connections, and tabulated with great care, show that the actual time
is 23 seconds odd for a local call and 30 seconds for a junction call.
There is almost exactly 7 seconds difference between them. That is, a
junction call does not take longer than i more than the local call. That,
of course, gets rid of a good deal of the argument in favour of the
divided multiple board. If your junction call does not take longer than
30 seconds to operate, there is not a very strong argument against
junction working. As a matter of fact, having the relay system in use
uniformly, so that all the exchanges are worked on the same system,
and all the operators are trained to do the same class of work exactly,
there is practically very little difference between the completion of a
local call and a junction call.

Vol. 82. 54

Laws Webb.

834 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April 30th.

Mr. The question of handling very large numbers of subscribers has

Laws Webb, j^^^ solved in New York a good deal in this way, that a large number
of what you might call satellite exchanges have sprung up owing to the
use by subscribers of what we call private branch exchanges, the private
branch exchange simply consisting of a miniature exchange — it often
grows to be a pretty large one — on the premises of the subscriber.
That class of service was at first introduced to give a good service to
very busy subscribers. We found that a great many subscribers were
over-using their lines, and were blocking their lines entirely to the
inward calls. We persuaded those very busy firms to take a branch
exchange outfit consisting of a switchboard connected by a number of
trunks to the nearest exchange, and from the switchboard were extended
instruments to the different departments and offices of the people who
had to use the service. A trained operator was put at the switchboard,
and the whole service of that subscriber was handled through that
private branch switchboard. At first it was pretty difficult to get
business concerns to take up that class of service : it cost ♦more, and
they did not see why they should not use a telephone in the old way,
that is, working one flat rate line so that it was used almost exclusively
for outward calls and gave the inward traffic no chance at all. How-
ever, that private exchange system gave so much improved a service, and
handled the traffic of a busy subscriber so effectively, that it very soon
became popular, and now instead of having to push it by means of
canvassing, and so on, it has become the accepted thing, and there are
actually in New York in private employ, operating branch exchange
switchboards, about twice as many trained operators as there are in
the main telephone exchanges themselves. There are, I should think,
at a rough guess — I have not got the exact figures in my mind — approxi-
mately 30,000 stations out of 100,000 stations in New York that are
operated on private branch exchanges. That method of working the
telephone service undoubtedly largely helps us to solve the question of
dealing with very large numbers of subscribers. Where you have big
establishments, such as large hotels and large apartment houses, it
gives an admirable service, and it of course largely saves in the number
of lines required to serve a given number of telephone users. It is the
practice now in New York to build no large apartment house or large
hotel without putting in a private branch exchange with a telephone in
every apartment, and I think, in fact, the New York Telephone Company
has contracts for private branch exchanges to be equipped in hotels
that are not even yet built, so thoroughly is the use of the telephone
recognised in New York.
Mr. Giu. Mr. Frank Gill : Mr. Aitken's paper is somewhat unusual in that,

instead of propounding a definite problem of known factors, he gives a
somewhat speculative paper. But I do not think it is any less impor-
tant on that account, because it deals with a very large and difficult
subject, and even on the " cheap and nasty " plan his 115,000 subscribers
involves figures running into some millions. I should like to congratu-
late Mr. Aitken on the abiUty he has shown in handling his subject.
For reasons which are fairly obvious I prefer not to express any very
strong opinion one way or the other, but I desire to point out one or

1903.] AN EFFICIENT TELEPHONE SYSTEM: DISCUSSION. 825

two things which should be borne in mind by teliephone engineers who Mr. Gui.
contemplate putting in a divided board. In the first place I understand
there are only two divided boards in existence, one in St. Louis and
one in Cleveland, each for 20,000 lines. One most important factor which
conies in is time. Every telephone subscriber wants to get through
almost before he makes his request, and I doubt very much whether
there is anything in the commercial world or in the scientific world
which is cut quite so fine as ordinary telephone operating. The first
query which comes is this, I rather want to apologise to the Institution
for trying to introduce a new factor ; we have such a lot of factors that
one hesitates to bring in another one, namely, the time-factor. The
time-factor of a subscriber's line is, we know, roughly about 2*28 per
cent. ; the time-factor of a junction line — or, as they call it in New
York, a trunk line — is about 23*5 per cent. That immediately raises
the very important fact that, if you are going to extend copper, you
extend copper which will be used in one ratio or in the other. In
Mr. Aitken's Fig. i, I have assumed, taking out figures as far as I could
without knowing the conditions of the locality in which the exchange
was to t>e planted, that there would be 1 15,000 lines, which would equal
about 70,000 miles of metallic circuit ; there would be, in addition,
about 60,000 miles of metallic circuit for junctions. In Fig. 9, I make
out there would be something Hke 172,000 miles of metallic circuit for
subscribers' lines, and about 14,000 miles for junctions, a very consider-
able reduction. The difference, therefore, is 56,000 miles of metallic
circuit against Fig. 9, which is approximately about 1,000 tons of
copper. Perhaps telephone men will follow the point a little easier
if I say 183 miles of 306 pair cable. It is a serious item, which you
must consider, and see whether what you get is worth it. On the
intermediate distributing board there would be three divisions, two
of them extra. There would be probably something like 123 tons more
of copper on those two. The jumpers for the two divisions would be
extra. There would be also a whole lot of smaller details. The inter-
mediate boards would be each full size, and the main frame would be
larger. The line lamps, the line relays, fitted with a back contact in a
doubtful situation, would be more — I am sorry Mr. Swinburne has
gone, because I wanted to tell him that we no longer wind electro-
magnets with german-silver wire, if indeed it was ever done — there
would be also the keys on the instruments. Against these items — I
have not noted them because Mr. Aitken has covered them very fully —
there would undoubtedly be a large number of savings. Mr. Webb has
rather anticipated me in regard to the question of the ratio of junction
calls. In the paper (page 814) a problem is worked out which is based
on the ration of i ; 2. I make out that if one takes the ratio as i : 1*3,
instead of requiring 66 J sections one will only require 51 f sections.
The distribution on a divided board is much more difficult, because you
have to distribute each section of the intermediate board separately.
In calculating the average numerical chances of junction working, in
Fig. I we have 97 per cent. — that is, the chances of the call being an
outgoing call — and in Fig. 9, 89 per cent. ; but, of course, you have to
consider the direction of the traffic.

Mr. Gill.

Mr.
Harrison.

826 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April 80th,

I would conclude by one suggestion, that if , as I have endeavoured
to show, the length of the subscribers' line in a divided board system is
a serious item, and one which requires to be considered carefully, then
the same item also requires grave consideration in any attempt made to
bring two exchanges together in one building, where one gets all the
junction work and none of the advantages of the divided board.

Mr. H. H. Harrison : I have been very interested in the paper
which has been read, as the question of the adoption of divided
multiple boards interested me some five or six years ago, before
Mr. Kellogg brought out his important patent. Mr. Aitken seems to
have assumed that we all know the necessity for divided boards.
Briefly, it is, of course, that, as the number of subscribers goes up,
the multiple connections, or panel area, required to enable the operator
to communicate with any subscriber become so great that it is no

longer possible for one operator to complete the connection. Hence
this gave rise over the other side to what was called, I believe, the
"express" system. That consisted of two boards — one in which the
calls were received, and the other board, or B board, as it was called,
in which the connection required was effected. This, in turn, neces-
sitated call-wires between the boards and two operators for every
connection made. The divided board system, as described, is very
ingeniously worked out, but I think it might be found rather difficult
in practice. For instance, it is pretty certain that the number of
divisions would have to be limited to four, because with an ordinary
metallic loop no simple system of selective signalling is possible in
more than four ways ; and while I do not think it is too much to ask a
subscriber to select one of four buttons, any more than it is asking too
much of him to look up the number of the required subscriber in his
telephone directory, he might reply, if you ask him to make combina-
tions with four buttons — the telephone subscriber is rather an impolite
person — that he was not having any ; so it is pretty certain, therefore,
that that limits the number of divisions to four. I would point out
that the excellence of Mr. Aitken's divided board service might be
such that in course of time he would have each one of his four boards

1903.] AN EFFICIENT TELEPHONE SYSTEM : DISCUSSION. 827

beginning to grow unwieldy, as the early multiple boards did, and then Mr.
he would be in the same difficulty as the early telephone people were. "*

I therefore want to describe a system called the Duplex Multiple
Board, which was invented over the other side, I believe, one exchange
of which was worked on the system. As it requires a diagram to
adequately describe it, I will ask your permission to communicate the
rest of my remarks.

(Communicated.) In the duplex multiple system the subscribers are
divided into two groups, A and B. Each line terminates in a local jack
in the usual manner. The multiple jacks are of special construction.
They consist, as shown in the diagram. Fig. A, of two pairs of line
springs to which the A and B lines are connected respectively, and
the bushes are split to form the necessary testing circuits.

It is claimed for this board that its capacity can be increased to
double that of the ordinary type, the multiple area remaining the same.
It has, however, two serious disadvantages. Three plugs are required,
an ordinary answering plug and an A and a B plug ; further, care is
required in testing for the engaged signal to see that the right half of
the bush is touched.

It is, however, an interesting attempt to reduce the number of the
junction lines by increasing the capacity of the central exchange with-
out, at the same time, requiring a system of selective signalUng.

Mr. J. E. Kingsbury : I should rather have preferred, sir, that Mr.
somebody having more confidence in Mr. Aitken's system than I have ^°&'*'"^-
should have spoken at this stage, in order that "he might have had some
of the support which I feel he deserves, if only for bringing such a
paper before us. We have lacked telephone papers, and are therefore
very much indebted to him for the one which he has re^. I think,
however, there is some danger of our taking his paper too seriously.
I am not at all sure that Mr. Aitken has not brought this paper before
us as something for discussion, rather than for us to assume that he is
prepared to take the responsibility of the adoption of the system he
proposes in one of the world's capitals. I believe the system has not
yet been put into operation. It is something, therefore, of an experi-
ment ; and one of the world's capitals is the last place in the world
where any responsiWe telephone engineer would think of trying
experiments. For that reason I think we need not, as I say, con-
sider it altogether too seriously. But we must recognise the fact
that in the development of the telephone growth which must come we
shall need all the invention that we can get, and it is even possible we
may have to call upon the public to do what Mr. Aitken is perfectly
ready to allow them to do. But before we do that I feel that we must
exhaust many other sources of invention that we have not yet touched.
Let us consider what it is that Mr. Aitken proposes. He proposes that
we shall have a series of switchboards, on each of which a portion of
the jacks shall be multipled. We can get a better mental conception
of the arrangement if we assume a scries of boards painted difiEerent
colours ; we will call them red, white, and blue. Upon each of them
is a signal, which may be operated at the will of the subscriber by
pressing a selected button ; and under such circumstances we should

828 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April 80th,

Mr.
Kingsbury.

Mr. Gavey.

naturally make the buttons a series of similar colours. Press a red
button and you drop a signal on the red board, and so on. That is
what is called " selective signalling." We had such a system in con-
nection with the " ring through " system, adopted by Mr. Poole in the
early days at Manchester. There was one kind of indicator which
would drop by pressing a white button, and another kind of indicator,
a clearing indicator, which would drop by pressing a black button.
In those days there was only one line, but both poles of the battery
were utilised, one by the white button and the other by the black.
On the introduction of the magneto there was a somewhat similar
use of a single line, by sending an alternating current on one occasion
and a commutated current on another. That gave us an oppor-
tunity by magneto working of selecting either one of the two signals.
The introduction of metallic circuit working and central battery
working gave us an opportunity of four choices, and really there is
very little reason why, since a four party line is an easy thing to
operate, a four area system should not be utilised, working on the
common battery. Of course it involves a large quantity of abstruse
diagrams and a large amount of technical ability to work them out, but
in essence that is what it amounts to. Mr. Aitken has gone into the
question of comparative costs. I do not propose to follow that in any
detail ; it has already been done by other speakers. But I would like
to emphasise Mr. Webb's remarks in regard to the operation of the
system by the public. I anticipate that Mr. Aitken will consider that
his reliability on the public is not so misplaced as some of us think.
My impression is that a telephone engineer regards his subscribers
individually as not only men of very great sense and ability, but I am
not at all sure whether he does not consider them all Senior Wranglers.
The poHce regard the individuals of society as most law-abiding people,
but they have a method of dealing with crowds which leaves the
individual, and the law-abiding character of the individual, out of
account. The telephone engineer, in dealing with the public, has to
adopt a similar distinction between individuals and telephone sub-
scribers. It is perfectly useless for us to depend upon a member of
the public — perhaps an impatient man of business, whose telephone
call may mean thousands of pounds — to press ttie right button or do
the right thing at all unless it is absolutely the most simple thing. For
that reason alone I think Mr. Aitken's method of a divided board
cannot be expected to be put into operation until, as I say, other
methods have been exhausted. Why does Mr. Aitken suggest the
divided board ? Mr. Kellogg suggested it probably ten years ago.
He suggested it when the limitation of the multiple board was about
6,000 ; to-day it is 20,000, to-morrow it will be 30,000 ; and I see no
reason to assume that we should regard that number as in any way
within reach of the limit. All we can say at present is that the multiple
board has grown in its capacity with the requirements of the business.
I see no reason at all why we should assume that its progress has
stopped, and I think we may take it that in that direction inventive
ingenuity would be well displayed.

Mr. J. Gavey : Sir, I think Mr. Aitken has placed the Institution

1903.] AN EFFICIENT TELEPHONE SYSTEJI : DISCUSSION. 8fl9

under a debt of gratitude for having brought this very important Mr.Gavey.
matter before it to-night. Many of the speakers who have preceded
me have made remarks which in some cases have anticipated my own.
In reference to certain criticisms I should like, however, to say that we
have not reached anything like finality, and that we ought to, and we
do, welcome every attempt that is made, or every suggestion that is
brought before us, with a view of improving the telephone service of
the country. The problem which is ever present to the mind of the
telephone engineer is simply this — to place the subscribers in com-
munication in the shortest possible interval of time, with a due regard
to a reasonable capital expenditure, and by the employment of the
fe^rest possible number of operators. This problem has been ever
before them, but as new devices have been introduced which appeared
to simplify the problem the difficulties have increased, owing to the
growth of the population and the growth of telephone subscribers.
As the last speaker said, it is only a few years ago when the multiple
board was supposed to meet the requirements of a given locality with
a capacity of 6,000. Now a multiple board of 15,000 is actually in
existence. A 20,000 board is designed, and that is still far from
meeting the requirements of the public ; and if anything in the nature
of Mr. Aitken's proposal — which certainly is an honest endeavour to
meet the difficulty — can be adopted, then I say he is conferring a
benefit on the community in bringing the subject forward. The
divided multiple boards that have been used in America can hardly be
said to bear very seriously on the problem, because they do not provide
automatic signalling — ^at least those that I saw did not. They are all
the old type, involving ringing up and ringing off, and whatever may
be said for or against them there is very little in common between
them and those proposed by Mr. Aitken. Mr. Aitken's statistics are
not universally applicable ; some of them have been referred to by
other speakers. With reference to others, I should like to point out
one or two matters, not in a carping spirit, but merely with a view
of preventing any misunderstanding. The author has made certain
definite statements as to the number of subscribers per operator, the
work carried by junctions, the time in getting through, etc., etc. I
should like to |>oint out that you cannot determine these factors
directly without first of all postulating the number of talks per sub-
scriber and the type of apparatus that you are using. In the first
place, with reference to the apparatus, I do not think you can make
any definite comparison between the old type of ringing on and ringing
off and the modern type of automatic signalling. I have a very firm
conviction that the introduction of automatic signalling, in which you
merely remove the telephone to call and place it back to clear, in
which the signalling on the junctions is wholly automatic, in which
the talking is reduced to a minimum, the operator simply being called
upon to ask for the number — and by the signalling she sees perfectly
well what is going on without intervention — I cannot help thinking
that with a system of that sort, a system which I think before many
years we shall see universally employed, the capacity of an operator
and the carrying power of the lines will be absolutely doubled. I

830 AITKEN : DIVIDED MULTIPLE SWITCHBOARDS : [April 30th,

Mr. Gavey. must confess that I have some sympathy with certain of the speakers
on the question of reducing the work of the public to a minimum. At
present, with the automatic system, that is absolutely minimised. Tell
it not in Gath, but I also am a telephone user, as well as being con-
nected with the engineering branch of the Post Office telephones. I
happen to have on my table a little switch with three keys. I am
frequently called to the telephone when immersed in business, im-
mersed in thought. I think at such a time that the telephone is a
nuisance, but I have to answer it. I answer it as quickly as possible ;
I put it down and go on with my work, and presently somebody rushes
in hurriedly and replaces the key, which I myself have forgotten to do.
I hope I am not an unintelligent user of the telephone, but I mention
that as one of the difficulties you have to contend with, apart altogether
from want of ability or want of care. When a very busy man who is
immersed in business, whose mind is full of very important matters, is
interrupted he just does what he has to do, and no more, forgetting the
little details that are involved in the special work of clearing off.

Mr. Aitken. Mr. W. AiTKEN, in reply, said : Mr. Webb made considerable reference

to the cost of the outside plant, but it is to be noted that in my schedule
of quantities I have shown how an increase of 550 yards on each of the
second 15,000 lines is obtained by the reduction in the number of
junction lines. It is also to be remembered that the great mass of
wires centralised on one great exchange will be cheaper per mile owing
to larger capacity cables being used and the decreased cost of labour in
laying. Mr. Dommerque, of the Kellogg Switchboard and Supply
Company of Chicago, takes a great interest in this subject, and I would
take the liberty of quoting some information given in correspondence
I have had with him. In a report made by him some years ago, which
is still valid as regards arguments but out of date as regards prices of
materials, he says : " As the cost of the installation of the wire plant is
not the item that is involved in the cost of telephone service, but the
annual expense, the interest and depreciation, maintenance and taxes
on the wire plant is the factor that must be taken into consideration
when comparing the preference of one system over the other." From
this he goes on to compare the two systems, allowing 0*35 miles of wires
per subscriber for the junction system, and 2*6 wire miles on the
divided system when dealing with one 10,000 line exchange against
four 2,500 line ones connected by junctions, and yet shows a result in
favour of the divided system. He concludes as follows : " It may be
of interest to note some points in which the single-office system
excels the multiple system outside of the monetary question. Neces-
sarily the condensation of all apparatus into one unit allows of the best
supervision and regulation of the system."

" More than anything else weighs the circumstance that each call in
the one-office system is handled by one operator only, which not only
allows of the highest speed in obtaining connection but also ensures
less mistakes than when calls are handled by two operators as it is the
case with the 60 per cent, or more calls that are trunked between the
four or more offices of a multiple-office system. Even with the best
trunking facilities it happens that in the multiple-office system during

19(^.] AN EFFICIENT TELEPHONE SYSTEM : DISCUSSION. 881

the busiest hours just when the trunks are most useful the service breaks Mr. Aitken.
down."

" Trunking requires more office cable and more contacts in the
talking circuit, and thereby deteriorates the transmission of speech.
The efficiency of apparatus like ringing machines, storage batteries
and their charging machines, is greater with one-office system, because
larger units are always more efficient and easier to maintain than
smaller units, certainly when the latter are scattered over several
pbu:es."

Mr. Dommerque in his letter adds : " I wish, however, to state that
with the introduction of ^^-inch and even J-inch jacks, large switch-
boards can be built without going to division-systems. In fact, we
would be able to build single division-boards for 25,000 subscribers.
This, of course, will also increase the range of division exchanges,
because, with these small jacks, we will be able to build division boards
up to 50,000 lines, using only two divisions, and correspondingly
greater, by using more than two divisions. The whole matter will sum
up in the advisability of having only one exchange in a city, against
several exchanges,"

With reference to the other points raised by Mr. Webb, particularly
that regarding the operating by the subscriber and which nearly all
succeeding speakers have also remarked on, I think too much is being
made of this, and that Mr. Webb is prepared to pay too much for
uniformity. Get a subscriber to understand that by performing a
certain act he will receive quicker attention with fewer possible
mistakes, and I am sure he will do it. He wants a quick and reliable
service, and is prepared to ;do anything reasonable to obtain it.
Automatic clearing is essential on such a system as I advocate, but
automatic calling is not essential on any system, in fact it may be looked
on as a doubtful facility. The absent-minded man may unconsciously
allow the lever of his desk telephone to rise and indicate a call, or
the charwoman or servant when cleaning remove the receiver to
more conveniently perform her duties, thereby giving the operator
unnecessary work and trouble.

It is to be borne in mind also that business men use press buttons — and
more of them, and often code-riming on each — in connection with bells
to call clerks, and when a mistake is made the man usually recognises
that he has wasted his own time and that of his clerk unnecessarily
and is more likely to be apologetic than use Mr. Webb's phrases.

The buttons might be coloured as mentioned by Mr. Kingsbury,
red, white, and blue, and all numbers in the book would be preceded
by one or other of these words, so that there would be no excuse for
mistakes. Why does a subscriber on the present system not ask for
Avenue when he wants Gerrard ? One is almost as likely a thing to do
as the other.

Mr. Webb thinks my values of calls too high — probably they are if
you consider only calls from one exchange to another, but what about
those that pass through one or two intermediate exchanges, which
take much longer ? The average is not very far out. I should like
further particulars of Mr. Webb's figures — figures have a bad reputa-

832 AITKEN: DIVIDED MULTIPLE SWITCHBOARDS: [April 30th,

Mr. Aitken. tion. The following will give an idea of the work required for the
two calls : —

LOCAL. JUNCTION.

(i) Inserts plug in jack over lamp (i) Inserts plug in jack' over lamp

glowing. glowing.

2) Pulls over listening-key and (2) Pulls over listening-ke)rs and
takes requirements from sub- takes requirement from sub-
scriber, criber.

(3) Tests line wanted, and if free (3) Presses call-key and repeats

inserts plug. number wanted to distant

(4) Puts key in through position. operator (may have to wait

(5) When cleaning lamps glow her turn or repeat number

withdraws two plugs. more than once).

(4) Junction operator allots line,

tests line wanted, and if free
inserts plug in jack.

(5) Presses ringing-key.

(6) First operator inserts plug in

junction jack.

(7) Pulls key to ** through."

(8) When cleaning lamps glow

withdraws two plug^.

(9) Junction operator withdraws

plug.

I find it difficult to understand Mr. Webb's reference to private
branch exchanges relieving the great centrals to any appreciable
extent. Very few firms in this country at least would care to pay
for an exchange line when a local private line would serve the same
purpose. There is certainly room for developing the private branch
exchange business.

With reference to Mr. Gill's remarks, for obvious reasons I could
not very well deal with a definite problem ; I should certainly have
preferred doing so, and have no doubt I could have shown even better
results. To the telephone engineer wlio would consider the points put
forward by Mr. Gill, I would say, Do not overlook the other points put
forward in favour of the divided system. As before mentioned, the
maintenance costs require careful attention and will be found to well
outweigh the capital costs. Mr. Gill's alarming figures of excess
weight of copper in my system are based on a hypothetical case, and I
believe have no sure foundation — at least are not sufficient to outweigh
the other advantages.

With regard to the percentage of junction calls, I think most sub-
scribers would be content to wait twice as long for a few calls to their
houses in the suburbs if they were assured of getting the great majority
of their business calls in the shortest possible time. If Mr. Gill
deducted the small exchanges from his figures the results would be
very different.

Mr. -Harrison's alternative system, judging by the meagre descrip-

1903.] AN EFFICIENT TELEPHONE SYSTEM : DISCUSSION. 838

tion given, is in my opinion practically unworkable. I believe he Mr.AUkcn.
means to put two subscriber's lines on one springjack by using
springs of different lengths and a split bush or test ring. On a 10,000
line exchange an operator could not test with certainty. When a call
was received for the B subscriber when a connection had already been
made by the same operator to the A subscriber, how would it be done ?
Would not the jack need to be enlarged to get in the six connections
and the necessary cable ?

I have some difficulty in understanding Mr. Kingsbury's opening
remarks. I have not read my paper to provoke discussion, but to
describe a system I believe capable of providing an efficient telephone
sjrstem for the world's capitals. The system is beyond the experimental
stage in at least the two divisions — in that there is nothing untried, and
only in one of the great cities can the experiment (if experiment it can
be called) of introducing it be efficiently tried — and when some engineer
or corporation with sufficient courage does adopt it I have no fear of
the result.

Mr. Kingsbury refers to Mr. Poole's system used at Manchester •
some years ago. The idea was excellent — the push-button arrange-
ment had, I understand, nothing to do with the partial non-success of
the system, but the weakness lay in the polarised ring-off indicator.

Mr. Kingsbur/s four-area system is altogether too vague to allow of
its being considered here.

W^hen writing my paper I overlooked a patent taken out by Mr.
Kingsbury's Company on June i, 1900, for divided boards on a some-
what similar system to mine, but instead of using two push-buttons, two
instruments were to be connected to the line at the subscriber's office.
This is open to all the objections of the push-button.

I have to thank Mr. Gavey for his kindly remarks. I agree with
him as to the object to be aimed at in designing a telephone system.
There is no doubt the ideal system should have all subscribers in the
same telephone area in one exchange. In the world's capitals this,
with our present knowledge, is not possible, but the nearest approach
to it should certainly be made. To the various features necessary for
quick and reliable operating mentioned by Mr. Gavey I would add the
reduction to the minimum of junction working with complicated
circuits and the necessity for the repeating of numbers by operations.

The President announced that the scrutineers reported the follow-
ing candidates to have been duly elected : —

Members.
Harry ColHngs Bishop. | Edmund Munroe Sawtelle.

Associate Members,

John Arnot Anderson.
Albert Arthur Blackburn.
Charles William Dawson.
John William Dawson.
Axel Carl Ludwig Ekstrom.
Rudolph Goldschmidt.

Edward Peter Grimsdick.
Harold Aislabie Howie.
William Arthur Molyneux.
Sidney Cuthbert Sheppard.
Arthur Dcnby Smith.
James Herbert Targett.

834 DISCUSSION ON ELECTRIC WIRING. [Glasgow, 1903.

Associates,

Leopold Charles Benton.
George Henry Broom.
William P. Dunne.
Arthur Herbert Flemming.
Algernon Coste Gilling.

Percy James Haler, B.Sc.
William H. W. James.
Harold Morton Middleton.
William Carmichael Peebles.
Alexander Russell Walker.

Students,

Algernon Edward Berriman.
Geo. Bradwell.
Ernest Phillip Elwin.
Herbert Geo. Jenkins.
Alfred Montgomery.
Stanley Robert Mullard.

Patrick F. Myers.
James Parkinson.
Alfred William Scrooby.
Arthur Douglas Taberncr.
John Dodsworth Walker.
Arthur Ward.

GLASGOW LOCAL SECTION.

DISCUSSION* ON ELECTRIC WIRING UP TO DATE.
(i4/ Meeting held January 13//1, 1903.)

At a discussion on the above question which was opened by Mr.
Chamen, attention was drawn to the number of outbreaks of fire which
had occurred owing to bad wiring, which were attributed to the use of
metal sheathed tubing with slip joints.

The opinion was expressed by Mr. Chamen and subsequent speakers,
that this class of protection for wiring had not answered anticipations,
and in fact it was doubtful whether it was as safe as wood casing.

Where iron tubing was used it was proposed that it should be made
with screwed joints throughout and earthed.

• For a fuller account, see The Electrical Review^ vol. Hi., p. 329 ; TTu
Electrician^ vol. 1., p. 1071.

835

NEWCASTLE LOCAL SECTION.

METHODS OF SUPPORTING AND PROTECTING
INSIDE CONDUCTORS.

By O. L. Falcon A R, Associate Member.

(Paper read at Meeting of Section^ January 19, 1903.)

Introductory, — In order to meet with the exigencies of the gradually
increasing pressure of supply, and also to cope with the demand for
more reliable and less expensive methods than those at present used, it
is imperative for electrical engineers constantly to recur to a subject
which has ultimately a most important bearing on the success of any
electrical undertaking. In view of the general tendency towards standard-
isation in electrical apparatus which has been a prominent feature of the
last decade, it is remarkable that " methods of supporting and protecting
conductors " should remain in such an undecided state. Possibly this
may be in some measure owing to the small amount of attention the
general body of electrical engineers have given this subject, and to
their confining their efforts more towards reducing the cost of produc-
tion and distribution of electricity. That an improvement in the present
methods is necessary is clearly shown by the excessive amount of
labour required to carry them out ; moreover, the cost of wiring
appears to be increasing rather than diminishing, and this, in the face
of recent vast improvements in gas-lighting, threatens, unless remedied,
seriously to curtail the advancement of the use of electricity. As far
as the author is aware, previous papers bearing on this subject have
chiefly been confined to the discussion of some particular system advo-
cated by or associated with the writers ; hence the subject has not per-
haps been considered in as broad a light as from the standpoint of
a person who has in most instances to decide what method he will
adopt, and is also held responsible, both morally and pecuniarily, for the
good working of the undertaking. The author hopes on this occasion
to consider as many as possible of the present systems in use, with the
object of deciding which is the most efficient and economical method
to be used for the various conditions required, and in order that this
may be done he trusts that any member who may be familiar with
systems not treated on in this paper will at the close take part in the
discussion. As the conditions under which the conductors will be
required to work ought to determine which system is requisite, it should
be possible to divide them into various groups and to standardise
to as large an extent as possible the method to be adopted for each
case. The author has, therefore, endeavoured broadly to classify the
conditions usually met with under the following headings : —

(A) Exposed Positions. — This may be considered to apply to the

836 FALCONAR: METHODS OF SUPPORTING [Newcastle,

wiring of very rough places — for instance, certain parts of shipyards,
boiler shops, forges, collieries, etc., where damage to the conductors
from mechanical injury, dampness, corrosive salts, gases, or other
causes have to be provided against.

(B) Ordinary Positions, — Or places where damage from outward
mechanical injury to any great extent is not to be apprehended, but
protection against general dampness, vapours, corrosive salts in plaster,
etc., must be allowed for. Instances of this class occur in all new
buildings, mills, warehouses, and workshops.

(C) Unexposed Positions, — Or places where no deleterious effects
other than the actions of the atmosphere, and general deterioration
owing to ordinary wear and tear aVe to be encountered. Such condi-
tions are met with in certain offices, shops, dry goods manufactories,
etc.

The author does not wish it to be supposed that he considers the
above classes should be made to embrace the whole of the conditions
met with in practice, but in order to avoid the introduction of a subject
which in the limited time at his disposal would be impossible to discuss
fully, he has taken them as a basis on which to work.

CLASS A.~EXPOSED POSITIONS.

The requirements, then, in regard to the methods of supporting and
protecting conductors for Class A may be briefly stated as follows : —
The conductors must be rigidly supported throughout their entire
length and protected by a substance which will withstand continual
rough usage ; they should, moreover, be protected from moisture and
be capable of being added to or withdrawn without undue inconvenience.
It is obvious that such substances as wood casing, insulating cleats, or
any form of split tubing would be unsuitable for this class, and one of
the commonest methods is to draw the wires into " iron gas-barrel."

Iron Gas-Barrel.

This, no doubt, has been, and is, in many instances, used with
success, but there are many objections to this system. Lack of flexi-
bility, interior roughness, extreme difficulty in preventing damage to
wires in drawing in, and rapid deterioration of cables owing to internal
moisture, are some of the principal ones. As the question of cost of
each system will be considered later, this may at the present moment
be ignored.

The difficulties which arise, especially where tubing of large dia-
meter has to be used, in getting round irregular-shaped bodies with
any pretence of neatness, will be appreciated b}' any one who has
had experience in the wiring of motors used for driving large power
machines in this class of conditions. Standard bends, elbows, and
tees can in many instances be used, but where special bends are
required for these purposes they waste an enormous amount of time
and patience.

1903.] AND PROTECTING INSIDE CONDUCTORS. 837

Interior Roughness.

The ordinary class of gas- or steam-tubing is, moreover, unsuitable
for use as a protection to any but armoured cables owing to the
interior roughness which invariably exists. This cuts through the
covering of the cables when they are drawn through, and in time
causes an endless amount of trouble. Tubing should only be used
after having an iron rod of nearly the same diameter as the inside of
the pipe driven through, and the ends should also be rimered to
remove any sharp edges after this is done. It is important that
insulating bushes of hardwood or other suitable substance should be
fitted at the point of entry or exit of cables from any kind of metallic
piping, and the author has records of numerous breakdowns of wiring
owing to neglect in attending to this very simple precaution.

Screwing.

The screwing of this class of tubing, besides taking a large amount
of time, is another source of danger to cables. The oil used for
lubricating the die, unless carefully wiped off the tube, is very apt
to get on to the cables, and plays havoc with any type of rubber
coverings. The sharp edges left on the . ends of the tubes after
screwing are also likely to be overlooked and to puncture the insulation
of cables. Though it may be thought these objections arise only
where careless workmen are employed, yet they must always be guarded
against, and with the class of workmen usually procurable extreme
care is more than can be expected. Packing cables owing to the use
of too small diameter of tubing is a great cause of damage. The
author has found that tubing of less than } in. inside diameter is little
use in the case of a draw-in system where looping is substituted for
jointing.

Jointing.

In jointing this class of tubing a watertight joint is not obtained
so easily as is apparently supposed by many— viz., by running a few
threads into a coupling without any form of packing. In moist
places, no doubt, rust will in time help to fill up any crevice ; but where
cables are led amongst machinery and in places where oil is likely
to be scattered about, great care has to be exercised to avoid this
finding its way through loose. couplings. If red lead is used, it should
be kept well off the end of the tube to which the coupling is screwed.
Tarred spun yarn or asbestos twine appears to be suitable for making
water-tight joints, but the author is not aware if they would resist oil.
Possibly lead wire would be suitable for this purpose.

Internal Moisture.

The deterioration of cables through internal moisture produced
by condensation is a defect common to all metallic tubing methods,
and often causes serious faults to develop after the installation has

838 FALCONAR: METHODS OF SUPPORTING [NewcasUe,

been working for some months. Whilst much of the moisture
attributed to this cause finds its way from the outside through imperfect
joints, in numerous instances which come under the author's notice this
has undoubtedly been the cause of trouble. In long vertical runs,
terminating at a switch or fitting, water often collects, and develops
an earth or short-circuit. In horizontal runs it collects at bends or
dips in the pipes, and the cables often break down at these points.
There are three methods of overcoming this : (i) drainage holes or
traps may be adopted, and the pipe given a slight fall to these
positions ; (2) the wires may be lead-covered or enclosed in some other
suitable watertight covering ; or (3) the tubing may be coated with a
non-conducting substance such as paper, which is said to prevent the
formation of moisture by condensation, this tubing being generally
of welded steel of thinner gauge than ordinary gas-barrel. {Note. — The
author has not heard of ordinary gas-barrel being coated with an
insulating substance, but possibly this may be procurable.) The author
believes the second method is to be preferred, as it is impossible to
prevent moisture collecting in some parts of the tubing, in spite of
drainage boxes or vents ; and the third method, besides providing
a porous substance which may, if water finds its way into the tube,
remain damp for a longer period than an unprotected pipe, destroj's
one of the greatest advantages of iron pipe work — viz., the prevention
of unnoticed leakage by immediate dead earthing, and consequent
warning by the blowing of the fuse protecting that circuit.

Welded Steel Tubing.

Heavy-gauge, uninsulated, welded steel tubing of smooth interior
can be obtained at a slightly higher cost than ordinary gas-barrel, and
this overcomes the difficulties due to roughness. Other disadvantages
arise, however. The thickness of the tubing is hardly enough to allow
of a ** Whitworth " full standard thread being cut, so the makers supply
special dies cutting a much finer non-standard thread, which is a great
inconvenience to users, especially as each maker recommends a
different type of thread which he has found, after careful experiment,
to be exactly suitable for the purpose. This seems like retrogression,
and reminds one of the old days, when each engine builder manufac-
tured his bolts and nuts with a special thread, so that future repairs
would have to come his way. It seems unfortunate, also, that more
uniformity does not exist in regard to the diameter of this class of
tubing. Some makers apparently take the inside measurements,
others the outside ; some take the diameter in millimetres, others in
fractions of an inch ; whilst some disregard both, and arrange their
tubing alphabetically, such as A size, B size, or C size. It is un-
necessary to enumerate the benefits which would result if uniform
dimensions were adopted by every maker, but possibly the makers
themselves realise that any form of heavy screwed piping at its best is
a superfluous and expensive method to adopt, and expect it to be
superseded sooner or later by some simpler and more easily fixed
system. One method which suggests itself to the author as a substi-

1908.] AND PROTECTING INSIDE CONDUCTORS. 839

tute for iron piping in this class is the use of " armoured cables." In
the author's opinion the protective substance should form part of the
cable itself, and if this were of sufficient strength, the cables might be
clipped on to the surroundings in the same manner as in an ordinary
gas installation. There is, of course, nothing new in this proposal.
The advocates of concentric wiring have endeavoured to introduce a
system similar to this for years, but judging from the small amount of
this class of work done at present (inside buildings), it is apparently
not desirable to alter the present system of double wiring. There is
no reason, however, why two armoured conductors should not be run
in buildings of this class in the same manner as is done in most ship
installations. In ship wiring this method has been used for some time
with considerable success in positions in this class, and also in classes
B and C.

CLASS B.— ORDINARY POSITIONS.

In Class B, though the risk from damage by mechanical injury
may not be so great, the dangers due to the other causes referred to —
viz., general dampness, moist vapours, corrosive salts in plaster,
etc. — often cause much trouble in practice. It is often desirable in
this class that the conductors be enclosed in plaster or concrete, con-
taining a considerable amount of moisture and often corrosive salts.
In such cases, the author has found any kind of split tubing without
watertight joints very unsatisfactory, and faults often occur after
installations of this nature have been completed and running for a
few weeks. Of the present methods in use, the welded steel tubing
already referred to, with screwed unions, appears to give the best
results, and the cables should be drawn in after the tubing has been
fixed complete, and the surroundings have become as dry as possible.
Draw-in or inspection boxes have, of course, to be fitted in this case,
and much inconvenience will be avoided in the future if these are left
easily accessible so that cables can be withdrawn if desired. If let
into plaster work, their lids should come flush with the outside layer,
and should have some distinctive marking, or if under floors, a trap
should be left to allow of easy access, and at the same time to
mark their position.

Brazed Steel Tubing.

Steel brazed joint tubing has not been found satisfactory by the
author. The brazing is often badly done, and splits at the least provo-
cation. In this class of tubing, as with iron gas-piping, great care
must be exercised in removing all burrs or sharp edges after cutting
and screwing, also in insulating pipe ends and allowing ample room
for conductors. The author has found in some instances that cables
which were drawn into tubes with little difficulty required a consider-
able effort to withdraw them after a few years' time owing to the inside
of the tube becoming rusted. If all elbows or sharp bends are strictly
prohibited, however, the difficulty in drawing in or out is considerably
reduced, but if unavoidable, they should be of the inspection type,
Vol. 82. 66

840 FALCONAR : METHODS OF SUPPORTING [Newcastle,

Wood Casing.

Wood casing, if well coated with shellac varnish, or other water-
proof composition, may also be used in this class with success, but
non-waterproof casing should \never be used, owing to the objections
already referred to in the case of insulated metallic tubing ; and with
wood casing, owing to its inflammable nature and there being no
metallic sheath, these objections have much greater significance.
Since the increase of pressure in the Newcastle district the author has
heard of numerous instances of slight fires occurring through the use
of unprotected casing in this class, aud one which came under bis
notice, and was, curiously enough, in a fire insurance company's office,
demonstrates clearly that even a well-designed installation is not per-
fectly protected from a fire occurring from this cause. In the case
referred to a leakage to earth of not more than one or two amperes at
240 volts was sufficient to make about 3 in. or 4 in. of i\ in. diameter
casing incandescent, and had any inflammable material been near at
hand the result would probably have been a serious fire. This circuit
was protected by a fusible cut-out on each pole. The fuse wire
consisted of No. 22 gauge lead wire.

Nox-Metallic Tubing.

The use of non-metallic tubing for inside conductors has, rather
strangely, not made any great headway during the last few years. In
the case of new buildings, earthenware tubes or ducts let into walls
during erection would, the author thinks, make an excellent system
of protection if this could be carried out to satisfy the requirements of
a modern householder. This he is afraid, however, would not be easy
to do, as the exact positions and arrangement of lights would obviously
have to be fixed before the building is up. It would also be a difficult
matter to fix additional lights after such an installation is completed,
and the cost is probably much greater than that of metallic tubing.
For factories and warehouses, however, these objections may not
apply to such an extent, and the author would be glad to hear if
any member has tried such a system.

BiTUMENISED FlBRK TUBIXG.

A few years ago this was said to be the coming thing. Among the
numerous advantages ascribed to it was that it was "impervious to
moisture," "fireproof," and "rat-proof." The first and second are
certainly not precisely accurate, as the author has on several occasions
come across pieces of this class of tubing which have become quite
'* pulpy" after being a few years in a damp position, and it is fairly easy
to ignite a piece of this tubing at a fire. It is evident, however, that
for a short time this tubing will resist moisture, and it is also doubtful
if any heat likely to arise from electrical causes would make it take tire,
so in many respects this tubing shows distinct advantages over wood
casing. The author has not tested the "rat-proof" qualities of this
tubing, but is quite prepared to admit of its being offensive to the

1903]

AND PROTECTING INSIDE CONDUCTORS.

841

digestive organs of Ithis type of rodent. Tlie greatest objection to
bitumenised fibre tubing is its brittleness. A slight blow with a
hammer, given accidentally when fixing, splinters it, and it cannot be
bent -to any appreciable extent. The
method of jointing by means of thin
brass sleeves is also defective, and tee-
pieces and draw-in boxes seem un-
known. It has already been noted that
it is desirable and often imperative for
the cables to be surrounded by a con-
ductive sheath, so it is doubtful if any
systems which do not fulfil this condi-
tion will ever be universally adopted,
unless the insulating properties of the
supporting or protective medium can be
so absolutely relied upon that the use of
insulated conductors is unnecessary.

Insulators.

The foregoing remarks bring before
our notice the use of insulators. These
form an excellent method of supporting
cables, and give protection from leakage
due to moisture, but, of course, form no
mechanical protection. In many cases,
especially in workshop wiring, cables
can be carried (except where led to or
from distributing boards, motors, or
lights) at such a height from the ground
that 1 all possibility of damage from this
cause is avoided. Insulators in these
instances are eminently suitable, and
by reducing the cost of erection greatly
enhance the " break-up " value of the
installations. The various forms of
insulators used and methods of fixing
are so well known, that comment is
unnecessary. A word may be said,
however, in regard to the securing of
heavy cables of 0*4 in. diameter or
larger. These should be laid on a
suitable grooved insulator, fixed so that
the weight of the cable is carried directly
by the insulator and not by fastenings,
which are likely in time to wear or get
eaten through and break. Exception to
this, however, may be taken in regard to underground colliery workings,
where it is sometimes advisable to have the cables secured in a com-
paratively flimsy manner to avoid them being broken or damaged by

Fig. I.

842 FALCONAR: METHODS OF SUPPORTING [Newcastle,

falls from the roof. Porcelain buttons or cleat insulators in two halves,
which grip the cable when screwed up, are very useful for small wires,
and seem likely to come into use to a large extent in the future. A
common fault in most of the cleat form of insulators is the exceedingly
small screw holes allowed ; this, however, is a matter which can easily
be rectified by the makers. In large iron buildings without any wood-
work, such as shipyard sheds, etc., not a little ingenuity has sometimes
to be displayed in the fixing of insulators to the surrounding iron work.
In an installation recently carried out by the author's firm at a large
engineering works on the Tyne the mains were carried across the tie-
bars out of the way of the travelling cranes by means of ordinary
double-shed insulators fitted with special clamps instead of bolts
(Fig. i). These are very easily fixed, and make a sound mechanical
job. All kinds of varieties of these clamp insulators can
^ be obtained. Wooden battens bolted to girders or

^ columns, or iron brackets, such as shown on Fig. 2, may
0^ be used for securing the smaller wires when button
0 insulators are used. There is another advantage to be
^ derived from the use of insulators — viz., the wires can
^ be traced by the eye and faults generally seen. More-
^ over, when discovered, they can be easily rectified
-V- ^ without having to withdraw the wires from tubes or to
^^^ cut open walls or floorings, etc. Although, at present,
] ^ insulators are used only for workshops or plain build-
\0 ingSi the author sees no reason why a modified form
0 should not be used for better-class buildings and private
^ houses. On the Continent the author understands a

Fig. 2. large amount of lighting wiring has been carried out by

means of twin flexible wires supported by insulated clips.
This method would certainly reduce the cost of the wiring considerably,
and if twin conductors heavily insulated were used instead of the
ordinary thinly-insulated flexible, this system should be perfectly
sound.

CLASS C- UNEXPOSED POSITIONS.

Our old friend wood casing, which has been in existence since the
earliest days of the commercial application of electricity, has on several
occasions been condemned as obsolete by eminent authorities. In
spite of this, however, it still exists, and, personally, the author regards
this method as being equal to many at present used for this class.
While the objections referred to in Class B condemn it in any but
perfectly dry places, in old buildings, especially large houses and
offices where it would be inconvenient and difficult to place the wiring
out of sight, casing is still an easy method of enclosing conductors, and
makes a neat-looking job.

Split Tubing.

Light gauge tubing of the " Simplex " class, with what is termed
** close " joint, but which the author would prefer to call " split tubing,"

1903.] AND PROTECTIKG INSIDE CONDUCTORS. 843

as the term " close " joint is certainly inclined to be misleading, is also
used in this class, and is regarded by some as a more mechanical
system of wiring. The tubing being jointed by being simply pressed
into tapered couplings, enables it to be fixed at about half the cost of
screwed joint systems. This class of tubing, however, requires rigid
support, as it is very much inclined to work loose, especially at bends
and tees, and this gives the job a very shoddy appearance. Saddles
should always be used in preference to pipe hooks for this purpose.
On the whole, the author does not think this system has much to
recommend it, except, perhaps, that it can be fixed by less highly-paid
men than can wood casing.

Lead-Covered Wiring.

Lead-covered cables clipped direct to surroundings by brass saddles
is, in the author's opinion, a much better method than either of those
referred to, and combines the advantages of simplicity, reduced cost of
'erection, immunity from moisture, and easy localisation of faults.
From an aesthetic point of view this may be objected to, but if the
wiring Is carefully carried out and runs kept perfectly straight without
sagging, the appearance is as good as wood casing or tubing on the
surface. Some excellent work of this class has been done in ship-
lighting, and probably the reason why this method has not been more
generally adopted for buildings is to be found in the conservatism of
fire office officials, and, one might also add in some instances, supply
companies' regulations.

Flexibles.

The protection of flexible conductors in unexposed places, is,
perhaps, more a question for cable manufacturers, as it largely depends
on the materials used for covering them. In exposed places, however,
this matter sometimes needs special attention. It is desirable in such
cases to limit the amount of flexible used as much as possible, and the
vast improvements, or, perhaps, one might call it enlightenment of the
electrical fittings' manufactuiers during the past two or three years, has
led to this being practicable with any fittings likely to be used in
this class. Portable lamps, however, are often required, and these
being probably subjected to more rough treatment than any other part
of the installation, faults frequently occur in the flexibles attached to
them. After experimenting with various kinds of armoured flexibles
for shipyard use, the author found that the ordinary workshop class
enclosed in flexible bronze or steel gas-tubing gave the most satis-
factory results, and, with the exception of being somewhat costly, this
method appears to be suitable in most instances where extremely rough
conditions are experienced. In ordinary cases armouring composed
of galvanised steel wires or steel braiding is sufficient to protect the
flexibles from being cut or damaged by rubbing against rough bodies,
but as oil has a very rapidly destructive effect on them, the tubing
method will be found much more reliable if there is any chance of the
cables coming in contact with the substance.

644 FALCONAR: METHODS Of SUPt>ORTlNG AND [NewcasOe,

Question of Cost.

In ascertaining which is the most suitable method to be adopted in
each class, the question of cost demands careful attention. Reference
has already been made to the excessive cost of erection ; in some
instances this very nearly equals the value of the materials used. An
analysis of the cost of the various methods referred to in this paper
would, therefore, be interesting, but in endeavouring to obtain this
from actual instances, the author found it impossible to make anything
but a very approximate comparison owing to the great variations in
the conditions of the different cases. The figures, therefore, of the
accompanying table must be taken only as representing the average
cost per point for erection, support, and protection of conductors in
installations which have come under the notice of the author during
the past three years.

Approximate Cost per Point Single Light Wiring Inside
Buildings.

Method and Class. I Materials. I Labour.

8. d. I • s. d.

Iron gas-barrel A ■ 13 o 12 6

Screwed welded tubing A 13 6 | 10 o

Armoured cables A i 901 80

Insulators B . ^5 5 2

Painted wood casing B y 6 \ 60

Ordinary wood casing C 67! 60

Split steel tubing C 7 o* I 60

46
3 9

Lead-covered wires (clipped direct) C 59
Insulators (cleat type) C 5 6

Total.

s. d.

25 6

23 6

17 o

11 7
13 6

12 7

13 o
lo 3

9 3

It will be noticed there is a considerable difference in the cost of
erection between screwed and unscrewed tubing, the latter costing
about half as much to erect as the former. Whilst this is owing
partly to the amount of time taken in cutting and screwing the heavy-
gauge piping, it must not be overlooked that very unfavourable con-
ditions of working generally exist where this class of tubing is used.
When armoured cables have been used by the author, however, the
conditions have been similar to those in which screwed tubing has
been used. Thus it will be seen that a very considerable saving is
effected in the cost of an installation of this nature. In Class B the
additional labour required for screwed tubing compared with wood
casing or insulators is still noticeable. In Class C the cost of cleat
insulators and lead-covered wires clipped direct come very near to
each other, and both are easily removed if required. Conditions vary
so greatly in regard to the surroundings of electrical installations that
the author feels it would be imprudent for him to define any system
as alone being suitable for any of the classes referred to. Generally

i90S.] PROTECTING tNSIDE CONDtJCTORS : DISCUSSION. 845

speaking, however, he is of this opinion : That for Class A sonic form
of armoured cables will in the near future be adopted as a standard
for this class. For Class B he is of the opinion that for surface work,
waterproof painted casing, and for covered wiring behind plaster work,
screwed welded tubing are the most satisfactory methods. For Class C
either cleat insulators or lead-covered cables, according to cirH:um-
stances. Insulators other than this type may be taken almost as
a separate class and form, as already mentioned, a highly efficient
method in the class of buildings suitable for their use.

In the event of dismantling and taking down of conductors,
insulators undoubtedly stand as the method which gives greatest
facilities and highest value for old material, and this is sometimes a
matter of importance in carrying out an installation which is to any
exten ^of an experimental nature. Wood casing, though not as expensive
to erect as screwed tubing, is practically of no use after being taken
aown, and it costs more to dismantle than the value of material
recovered. Owing to the few instances he could refer to, the author
was unable to obtain any reliable data in regard to the cost of taking
down cables fitted in accordance with the methods referred to, but it
is obvious that with piping the conductors would be more likely to be
damaged or cut into short lengths than with armoured cables, and
consequently to be of less value as old material.

The author hopes these somewhat brief and incomplete descriptions
given by him of a few of the methods in general use will have been of
some interest, and he trusts that this paper may open the way to a full
discussion of the subject which will tend towards greater uniformity
in methods in supporting and protecting inside conductors.

Mr. J. H. Holmes {Chairman) said that the paper was one which Mr. Holmes
lent itself to a good discussion. As Mr. Falconar had mentioned his
name as having sent a board of samples, he would like to tell the
members how the tubing to which the author of the paper referred
was made, he having seen it manufactured both in America and
Germany. In the former country the interior conduit system was
largely used. The tubing was made out of long strips of paper rolled
round and round, one in one direction and another in another, until
the requisite thickness was obtained. The tubes were cut up and
dipped end-ways into an asphaltic composition. It was quite hot when
dipped, and it dried and formed very solid. He did not think tubing
got pulpy when made in this way. In America they found the tubing
liable to damage mechanically by people putting nails through it, and
they therefore provided it with a steel covering.

The American system differed from that of Germany, for in that
country Mr. Bergman made it on quite a different plan. He made the
tubing out of very good quality thin sheet steel, which, after bending,
was brazed. The steel tube was made a little larger than the asphaltic
tube, which was placed inside. The steel tube was then actually drawn
down on to the asphaltic tube (which was somewhat longer than the
steel tube), during which process the steel tube got smaller in diametei
and greater in length until the asphaltic composition made a very
firm lining.

B46 FALCONAR: METHODS Of* SUPPORTING AND [Newcastle,

Mr. Holmes.

Mr.

Woodhouw.

Mr. Xcwitt.

The unions were also a very fine piece of work, and were actually
cold-pressed out of sheet steel. The brass-covered tubing was similarly
made. Bends at any angle were easily obtained by the use of a tool.
He noticed Mr. Falconar suggested the use of lead wire for making
joints in the tubing, but he did not quite see how this could be used.

Mr. W. B. WooDHOUSE said that his experience of split tubes had
forced him to the conclusion that such tubing should not be used
where there was any moisture ; L-pieces should never be used.
He found a cheap construction was gas-barrel, screwed into cast-
iron junction boxes, w^hich, if properly supervised, could be made
watertight ; much of the trouble with internal burrs arose from using
pipes too small for the purpose. Wherever possible he preferred
to use clip insulators ; for small wires the button insulators were ex-
cellent, but the weak points of such wiring seemed to be at the switches
and ceiling roses, for with the fittings now on the market it was
necessary to mount these on wood. He suggested that these fittings
should be arranged like the clip insulators, so that a rose might be
fixed straight on to iron work and yet have the wires surrounded by
porcelain. With reference to the double-shed insulators, the speaker
disagreed with such construction, because it needed binding wire,
which he considered an abomination. He sketched a type of insulator
made by the British Thomson- Houston Company, which could be
mounted singly or in rows in a very cheap and effective manner : it
was suitable for all cables larger than 7-i8s, and although the cable
was firmly gripped by the insulator it was easily removed. With
reference to the use of flexible metallic tubing for protecting hand-
lamp leads, his experience had been that such tubing was not oil-tight,
and on account of its strong appearance got very rough treatment,
which caused it to break and cut into the lead. He preferred to use
ordinary workshop flexible, with a heavy outer coating of jute and
a protecting iron wire ; this was fairly strong, would stand a consider-
able amount of oil, and was cheap to replace. In places where much
oil was to be met with, lead-covered wires were the only wires that
could be used, but the oil always got to the end of the lead, at the
switch or lamp fittings, and he met the trouble by sealing in the
conductors in a porcelain or metal box, just as in a cable dividing box.
Mr. L. Newitt said he had very little to do with contract wiring
himself, but, at the same time, was anxious to know what others had
done. On reading over the paper he had not discovered that any one
of the systems described was perfect. For example, if we took any one
of the systems requiring steel tubing, we put ourselves very much in the
hands of the plumber or engineer, who had to screw and fit up these
pipes, and it was often found that a sharp rag was left on the piping,
which tore the insulation o£f the wires ; or the pipes were not water-
tight. Also, if piping were used, we had to consider the increased cost
of the installation which, when work was undertaken at about 12s, per
light, would not leave sufficient margin for doing really good work
with piping. It had also been noticed that in some cases condensation
in the pipes occurred, and then it was only a question of time before the
installation broke down.

1903] PROTECTING INSIDE CONDUCTORS : DISCUSSION. 847

With regard to the remarks on rat-proof cable, he had heard it said Mr. Ncwiit
that rats never bit tubing unless they heard water running inside of it ;
so that they need have no fear on that score.

With reference to t^e tubing which was insulated on the inside, it
was almost impossible to retain the insulation intact around bends
and joints where it was particularly required, and in fact any piping
that could be used did not appear to be entirely satisfactory.

As regards wood casing, he (Mr. Newitt) quite agreed with the
writer of the paper that, except in isolated cases, it was not to be recom-
mended. Personally, he thought that the more wires were exposed
the less likely they were to cause trouble, provided that at points where
they were liable to external injury they were protected by a suitable
guard. To illustrate how a system of wiring without casing or tubing
could be carried out, he had brought with him a complete model of
a section of wiring, showing how a friend of his had fitted up* his
building, and he trusted that some of the members would give their
opinion on the arrangement.

As regards this proposed system of wiring, it was possible that the
Insurance companies might have some objection to the arrangement,
but if the matter was thoroughly taken up by the proper authorities he
thought there would be no difficulty in getting the necessary addenda
to the rules of all insurance companies. This system was recom-
mended for its simplicity, cheapness, safety, the absence of all
soldering, and the ease with which extensions could be made if found
necessary.

Mr. A. W. Heaviside said that one gentleman had referred to Prof.
Silvanus Thompson's description of the ideal tubing, but he thought
he had left out the expressions pick-tight and hammer-tight. It
appeared to him that the most important thing was the insulation ; why
trouble about condensed moisture, except, perhaps, in dealing with
shipwork? A man who had had experience of shipwork could do
almost anything. With regard to the various methods, it seemed to
him that everybody was tr)ring to find out which was the cheapest, and
we should eventually settle down to three or four types. The greatest
problem of all was the bad workman, because his workmanship was
bad and he created a bad impression. He not only injured the house,
but had no regard for the comfort of the householders.

Mr. F. Little said he had had a good deal of wiring experience.
He noticed Mr. Falconar did not refer to the earthing of any system,
particularly of lead-covered systems. It was important, where the
ceiling roses and switches are fixed, that the lead covering should
be metallically connected by some means. He had used the single
lead-covered wire, and he thought it a very good system— especially
underneath floors, or in difficult situations where bends were numerous.
He was of the opinion that in all cases tubing systems should be
properly earthed. A little time ago two men were killed through
inefficient earthing of tubing. Had it been properly earthed this
would not have occurred. He thought the system introduced by
Mr. Bathurst was a very good one.

Mr. F. T. Hanks said that Mr. Falconar, in discussing gas-barrel,

Mr.
Heaviside.

Mr. Uttle.

Mr. Hanks.

848 FALCONAR: METHODS OP SUPPORTING AND [NewcasUe,

Mr. Hanks, had mentioned that it had a want of flexibility. If necessary to make
this flexible, it required a great deal of labour, which should be avoided
as much as possible on account of cost. In regard to internal rough-
ness, this tubing could now be obtained without this disadvantage.
It was not a practical suggestion to drive an iron bar through a gas-
barrel to remove the internal roughness. He could understand a
" rimer " or " cutter " being used for the purpose, but it would be
very bad for the "cutter." A man who was a mechanic should not
have any trouble in making watertight joints in gas tubing.

He did not understand how Mr. Falconar intended to use spun
yarn, asbestos twine, or lead wire in making watertight joints — unless
he used lock-nuts.

With reference to internal moisture, a solution of this problem was
very badly wanted. The life of a cable was no doubt shortened by
water getting into pipes. He could not suggest a remedy, unless it
were by lining iron or steel pipes. He thought that, if they were lined*
condensation would not be so likely to take place, as moisture did not
then come into actual contact with the internal surface of the pipes.
The threads which were put on the ends of welded steel tubing were
rightly condemned by Mr. Falconar. It was a great nuisance to have
to procure special tools in order to get the special threads required.
He did not think screwing at all necessary on many classes of in-
stallations. He thought ■ slip joints were quite good enough and
much less costly in cases where there was no necessity for much
strength, and would propose that the ends of the tubes and the
insides of the sockets be covered with a hard-drying varnish.
This would make a good and lasting watertight joint. There should
be no difiiculty in obtaining a suitable compound which would ensure
an electrical connection through the joints.

At the end of his paper Mr. Falconar favoured armoured cables for
use under Class A. What is wanted is a cable which would meet all
conditions in practical work, but the difficulty was to get an armoured
cable to meet the many requirements. For instance, it would not be
at all practical to use steel-taped cable if many sharp bends came into
the run, but he thought such a cable would be very serviceable for long
runs without many bends. Ordinary wire-armoured cabling answered
well for ship work, but it had the objection that if moisture, especially
sea-water, got to the galvanized steel wires, it deteriorated them in
time, and if examined after a while they were generally found to have
become a mass of rust. If armoured cabling were well painted, the
paint would afford protection for the iron armouring, and that in turn
to the internal part of the cable, and would make a lasting job. With
regard to non-metallic tubing, he did not think Mr. Falconar's sug-
gestion to run earthenware tubes or ducts, let into the walls, was a very
practical one, and he thought the question would have to be very care-
fully considered before this suggestion was adopted. Bituminous fibre
tubing was, he thought, rightly condemned. It was not a good material
at the best, and there was always the likelihood of nails, etc., being
driven into it. /

Mr. Falconar rightly condemned simplex, or split tubing, as/ he

1903.] PROTECTING INSIDE CONDUCTORS: DISCUSSION. 349

called it. He (the speaker) thought if tubing had to be used, it should Mr. Hanks,
be welded tubing — not split or brazed. He thought, where stronger
mechanical protection was not required, lead-covered wiring was one of
the best systems for carrying out an installation, as such wiring could
be made watertight more easily than any other system. He had in
mind an installation carried out in some extensive greenhouses, where
a lead-covered cable system was made absolutely watertight. A twin
lead-covered cable was used and worked admirably. The tin-lead
boxes into which the wires were brought had the leading-in holes
drifted so that the cables fitted exactly, but white-lead paint was
applied to the ends of the cables before being inserted. It made
a very neat installation, and successfully withstood the water. The
fittings, as well as the entrances to the switches, etc., were, of course,
made watertight.

He would have liked to see more reference made in the paper
to the protection of the conductors at the terminals, where the
switches, etc., came, because he thought breakdowns were in most
instances caused by faults, etc., at the terminals rather than in the
general run of the cables, and he rather wondered Mr. Falconar had
not given greater prominence to this point.

With reference to Mr. Falconar's remarks to the effect that a form
of armoured cable would at some future time be adopted as a standard,
he did not agree with the writer for the reasons stated. He did not
think an armoured cable would be manufactured that would meet the
many demands which cropped up in ordinary practice.

He was still very much in favour of wood casing for surface work in
dry places, but the grooves should be coated with shellac varnish and
the casing well painted on the outside. He wondered owners did not
take more care of their installations as regards the painting, etc., of
casing or cables generally. In many cases the ordinary woodwork was
seen to be well painted and the casings, tubes, etc., allowed to go with-
out any such covering.

For Class C Mr. Falconar favoured cleet insulators or lead-covered
wires. For his part, although he thought lead-covered wires would
make a very neat installation, he would not favour their use on plaster
work. He foresaw much trouble in fixing such cables because plugs
must be used in many cases. This would be costly as regards labour,
and a? tl^e cables would not cover the ends of the plugs the latter
would look unsightly.

With regard to the question of cost, he did not see why Mr.
Falconar made any reference to the value of the material after an
installation had been dismantled. If it were foreseen that the installa-
tion was to be of a temporary character, very little pains need be taken
in putting it up, but care would of course be taken not to injure the
material more than could be helped.

Mr. G. Ralph said one of the previous speakers mentioned having Mr. Ralph.
used flexible metallic tubing for wiring big engines. It might be of
interest to know flexible metallic tubing, made from solid drawn tube,
could now be obtained, which was of course impervious to oil and
water, and which would therefore seem very suitable for this purpose.

850 FALCONAR : METHODS OF SUPPORTING AND [Newcastle,

Mr. Mr. W. B. WooDHOUSE said that the tubing to which Mr. Ralph

Woodhousc. referred was about twice the price of the ordinary sort.
Mr. Gou-dy. Mr. S. H. GowDY was of the opinion that the time had not yet come

for standardisation. Each method had its advantages and would retain
them for some considerable time to come, but insulated steel tubing
would eventually be adopted, possibly a more flexible tube than we
are accustomed to use at the present. He considered that for damp
places, lead-covered wires in screwed welded tubes, or lead wires
in wood casing painted with shellac, made a very sound job. Non-
metalUc or papier mache tubing is of little use unless it can be fixed so
as to be absolutely free from the joiner's hammer. Ordinary wood
casing is not done with yet, and is probably still more used than any
other system for protecting wires. Plain uninsulated tubing has both its
advantages and its disadvantages. In case of the former, should a short
circuit occur between two wires of opposite polarity they will probably
burn themselves out and prevent any further danger ; whilst, in the
latter, dampness is not easily got rid of, thus increasing the trouble of
earth leakage, the sweating acting upoa^he insulation detrimentally.
Professor Silvanus Thompson had defined Sb-^eal system in a nutshell
when he said it should be electric-tight, water-iljght, air-tight, gas-tight,
oil-tight, and rat-tight. Therefore, what is ] required is a perfect
insulator mechanically strong and impervious ^o moisture, acids and
alkahes of cements and plasters used on building^ With reference to
the estimates and cost of the different classes c\f tubing and casing
mentioned in the paper, he would like to have fulltx details as to what
they include, and how Mr. Falconar arrived at them, ;>6 the price seemed
very high in some cases. He was of the opinion that screwed welded
steel tubing was the only satisfactory tubing yet introctuced, though it
was more expensive both in first cost and in erection. \He considered
there were far too many different patterns of tubing acces5ories, and that
there was a great want of standardisation both in these ai\d in the sizes
of tubing itself, and in support of this gave some details ejctracted from
lists of various manufacturers who seemed to vie with each^j other as to
which could provide the largest instead of the smallest Vnumber of
fittings. Some made use of outside dimensions, while otheirs only gave
internal measurements, while others again listed their gclods alpha-
betically.

Mr. A. E. GoTT said that there was no doubt some form of piping
system would be the system of the future. If there were mi itiple con-
trol and separate wires going to every lamp in the place, t liese wires
would have to cross each other, which would add to the dil ficulties of
installation. The weakness of any pipe system was the absei ice of any
recognised method of running pipes along the wall and unde f the floor.
The boxes of all these pipe systems seemed to be too shallc>w. Pipe
systems to be satisfactorily installed should be let into the o^rickwork
before the plaster was laid on. Lead-covered wires had failed) in many
installations because pure lead was used. Some lead alloy w«is wanted
to replace the silver in the old-fashioned lead. A lar'ie firm of
shipowners had taken out their entire lead-covered ins-tallations on
board their ships, and had used vulcanized wire with great success.

Mr. Gott.

1903. PROTECTING INSIDE CONDUCTORS : DISCUSSION.

851

Proctor.

He remembered the first system he installed, where the conductors Mr. Goti.
were buried in fireclay — to prevent them taking fire. They also used
casing three sizes too large. This was done most religiously. The
system was still running and there had not been a fire.

The success of any system depended largely on the question of
labour. The electrical trade suffered from imperfect labour. Every
man who was a failure in every other trade came to them, and thus
jobs were spoilt by ignorant men. He remembered the case of some
bad work on a ship. The cables were run along the lower deck,
were plain cotton covered without rubber or compound, and every
time a sea came down the companion-way there was a short circuit.
This vessel, which was an oil-tank vessel of the old type, was
destroyed by a terrific explosion, and a man who was in the hold at
the time had not been seen since. There was ncj doubt a spark caused
all the trouble.

Mr. C. F. Proctor said the question was really one of cost. He Mr.
believed that a cheap quality of iron pipe could be obtained from
manufacturers. He was also of the opinion that the architect was the
cause of much of the trouble, as he did not take into consideration the
wiring when designing the building. He knew of several cases where
great and unnecessary expense had been caused through this over-
sight, no attention having been given to how pipes could be run
without encountering thick walls, thus leading to the making of
numerous bends and joints which might have been avoided. On the
whole, he thought the iron pipes one of the safest and best methods. Mr. Robson.

Mr. R. RoBsoN said wood-casing was very hard to beat for old
houses, and it was certainly the thing for the poor man's house because
of its cheapness.

Mr. A. W. Heaviside said it was a very important question, as
where a public supply company expended capital to the extent of
;£ 1 00,000 the public had to spend ;£50,ooo on fittings, and that was
not in the case of a well-developed company. For every ;£i 00,000
spent by the company the public would probably have to spend an
equivalent amount in the wiring of their houses.

Mr. Falconar, in reply, said : The Chairman, at the last meeting,
made some comments on the tubing system. He would like to know
a little more about the method of drawing the tubing exhibited. Was
the steel covering drawn on cold ? [Mr. Holmes : " Yes.*'] Mr. Holmes
also made some remarks about the methods of jointing proposed.
With regard to asbestos twine, the idea was to wind it after the
tube had been screwed; if wound round the thread before sockets
were screwed on a fairly good watertight joint was obtained. Mr.
Woodhousc confirmed his remarks about simplex tubing ; he also
advocated ceiling roses without blocks. The worst part was where the
wires were run under the ceiling rose ; he had seen several ceiling
roses made with grooves or holes going through the porcelain base.
With regard to lead-covered wiring in flexible tubing, he had not tried
it, but imagined the lead covering would give way.

He had some ver>' scathing remarks to make to Mr. Sleigh, who
rather took the wind out of his sails by bringing a samole of standard

Mr.
Heaviside.

Mr.

Falconar.

862 FALCONAR : PROTECTING INSIDE CONDUCTORS. [Newcastle.

Mr. tube, from which he demonstrated that the apparent discrepancy in his

a conar. remarks was due to the present imperfect method of measuring gas

tubing. Mr. Sleigh recommended taped wires. He had tried these

once, but they were not very successful. The tape did not seem to be

sufficient and moisture got in.

Mr. Little made some remarks about earthing, and he entirely
agreed with him that any metallic tube system should be continually
earthed through the entire length.

He was obliged to Mr. Hanks for his long criticism of the paper.
With regard to the method of producing a smooth interior in the tubes,
he did not see how Mr. Hanks could get a cutter or rimer right through
a long tube.

With regard to jointing tubing, his reply to Mr. Holmes applied to
Mr. Hanks as well.

With reference to sleeve-joints, these would certainly be very good
where the piping was rigidly fixed, but he found them in most cases
apt to work loose (there was a sample on the board).

With regard to the sketch on page 841, it was not meant to repre-
sent petticoat insulators; they were bobbin insulators, and were for
inside, not for outside use. Mr. Hanks mentioned something about
junction-boxes lined with mica, but he had not had a very satisfactory
experience with it, as it absorbed moisture.

Regarding waterproof casing, his idea was to prevent the water
from getting in. He agreed with Mr. Hanks that good insulation was
obtained when the casing was shellac-coated, with a coat of paint over
all. In one case he had in mind the test came out excellently, although
the building was very damp.

The value of old materials was a point to be considered. If the
wiring could not be taken out, or was worthless when this was done,
the user would have to write off a large amount of the cost as estab-
lishment charges or otherwise. If there was some method by which
wires could be taken out easily they would then make a valuable asset.
Mr. Gowdy evidently thought screwed tubing the best. He would like
to know what sort of tubing Professor Silvanus Thompson suggested
after giving his definition of his ideal conductor.

With reference to Mr. Robson's recommendation of wood-casing,
his attention had been called to some remarks on this subject in the
Electrical Review, He was gratified to see they considered his paper
deserved the careful criticism they had given it, which, on the whole,
was favourable, but they mentioned he seemed to have a soft corner in
his heart for wood-casing. His experience of wood-casing had been
the same as Mr. Robson's, very favourable. They also condemned
him for having divided his subject into more than two classes ; one
class, the worst, was the only one necessary. But if you were to do
that, it meant practically abolishing the electric light from half of the
consumers who could not afford to pay the cost of wiring for this
class.

With regard to damp caused by bad state of property, this was a
matter for the property owners to attend to.

863

NEWCASTLE LOCAL SECTION.

SOME NOTES ON CONTINENTAL POWER-HOUSE
EQUIPMENT.

By H. L. RiSELEY, Associate Member.

(Paper read at Meeting of Section^ February i6, 1903.)

In response to your committee's invitation to submit a paper to
the Local Section, I have thought that a few notes on the subject of
Continental power-station practice gathered during a visit to the
Continent last September might be of interest, especially to those
who agree with the writer that there is much to be seen worthy of
consideration, if not . imitation — of course, subject to improvement.
Some little interest may also be attached to a few of my notes in view
of the Institution's Continental trip this spring.

On first entering a Continental power-station, one is struck especially
by the apparently extravagant amount of space which the switchboards
and accessories occupy in the majority of central stations abroad. On
closer inspection and consideration one finds that this is not without an
object ; the object being primarily to provide for any contingency which
may arise, and always to provide a duplicate method of operating in
event of any part of the switching apparatus being deranged by
accident.

A system nearly approaching the ideal was represented, in my
opinion, by the central station at Paderno, twenty miles from Milan,
which may be of interest, as it is to be visited during the Italian trip
of the Institution next April. There are seven turbine water-driven
generators, having a capacity of 2,160 H.P. each, and the machines a
capacity of 1,590 k.w. each, speed of 180 revolutions per minute,
frequency 42 per second, 13,500 volts. The current generated by
the alternators at Paderno is collected at the 'bus-bars, and thence
led to the high-tension transmission line without the intervention of any
transformers. At Milan the line ends at the Porta Volta station, where
the pressure is transformed down to 3,600 volts, and at this station
steam-driven generators are running in parallel with the transformed
current generated at Paderno (Fig. i).

The switchboard at the central generating station at Paderno is
arranged in a large central opening in the wall, covering an area of
1,750 square feet (Fig. 2). The apparatus for controlling the generators
is divided into nine panels, seven of which are for the seven generators,
and the two panels in the centre serve for collecting the two sets of
'bus-bars and for placing wattmeters, etc. The attached sketch shows
a complete diagram of the generator switchboard, board for the trans-

85i

RISELEY : SOME NOTES ON CONTINENTAL [Newcastle,

LINC.
LENGTH £0 MIL6d
N90F WIRES e.
DIA.H •• 9l?fn .

Fig. I.

mission line, and feeder panels at Milan. Each of the generator panels
comprises one triple-pole oil-break switch, three fuses, one linking-up
device, one rheostat for field, one rheostat for exciter, one instrument
transformer, one voltmeter and indicating wattmeter, one synchronising
voltmeter and lamps. All the machine rheostats can be worked in

1903.J

POWER.HOUSE^ EQUIPMENT.

855

MAIN
BOARD

TO TMAlJtrOAMeAS.

Fig. 2.

parallel or not as desired. The link devices serve the following
purpose : The whole of the installation from Paderno to Porta' Vol ta,
the auxiliary generating station at Milan, and sub-stations had to be
arranged so as to enable the two services to be separated at any moment
into two distinct systems. For that reason the 'bus-bars are arranged
in two groups, and each generator may be switched on either group ;
Vol. 82. 56

856 RlSELEY: SOME NOTES ON CONTINENTAL [Newcastle,

in that way the lines can be separated. The steam plant at Milan and
the generators at Paderno can also be separated. It was also arranged
to provide for the possibility of separating one of the services from
the other, in case that service should have any special requirements on
account of its disturbing influence on the other services. However, the
experience at Paderno has proved that it has not been necessary to
separate the two services. Behind the series of high-tension generator
panels are arranged in another room the high-tension transmission line
boards, each line having a special switchboard, with switch, link device,
voltmeter, and ammeter. All the switchboards are extremely accessible.
Each panel may be entirely separated from the live ones, so that it may
be attended to and cleaned by the attendant in perfect safety. The
panels are, as usual in Continental practice, made of marble and porce-
lain fixed on iron supports, no combustible material being used in their
construction. The connections are all rigid bars, and the whole is a
perfectly symmetrical, simple, and extremely mechanical job. The
high-tension transmission lines, before taken out, are led into the floor
above, in which are arranged the lightning arresters. Thence they pass
through holes in the wall to the first pole. The lightning arresters are
of the usual Wurz type, and comprise a number of cylinders made of
special brass containing a large quantity of zinc, arranged so as to leave
about 0*04 in. gap between each cylinder.

In my opinion the advantages of this type of board are its extreme
accessibility and safety in having, so to speak, another way round,
everything being in duplicate. Each portion of the apparatus can be
made dead for cleaning or overhauling purposes without the slightest
danger of interrupting the supply. The type of board which is the
favourite in this country for high-tension alternating work is sometimes
referred to as the multicellular type. The chief faults in connection
with this type of board are that it is too cramped, the 'bus-bars being
far too close together, and there being no second way round. Also, it
is very diflicult to keep clean, as the insulators at back of 'bus-bars get
covered in hot engine-rooms with a greasy deposit of dirt, which it is
impossible to remove by means of air blast, and it is obviously not very
safe to try and clean a live board by means of dusters, etc., as you then
stand a good chance of starting an arc between two bars, besides being
a danger to the man employed. Again, the switches are too cramped.
It is not an uncommon thing for the switchboard attendant when about
to synchronise to put the switch a shade beyond half-cock, and to make
contact to the bars with disastrous results.

Kander Power-house.

As the first full-gauge electric railway was supplied from this power-
house, I think a short description will be of interest. It is situated near
the junction of the Kander with the Simmen, quite close to Lake
Thun, and was entirely equipped by Messrs. Brown-Boveri. Its
primary object, as stated, is to supply power to the Burgdorf-Thun line.
At present about 3,600 H.P. are converted into electric energy, but

19030 POWER-HOUSE EQUIPMENT. 857

provision has been made for increasing the capacity of the station to
4,500 H.P.

The power-house is situated on the bank of the lake, and is 108 ft.
by 37i ft. wide, and has room for six turbines and generators— up to
the present five have been installed. The turbines are by Girard, of
900 H.P. each at 300 revolutions per minute, and the speed can be
regulated by hand or automatically. The three-phase generators are
connected direct to the turbines, having each a rotating field spider
with 16 poles, and develop each 620 k.w. at 4,000 volts. The drop is
18 per cent, up to 115 amperes at 4,000 volts on an inductive load,
necessitating an increase of 387 per cent, in the exciting current. In
view of the fact that the whole output of a machine has to be used at
times on a single-phase lighting circuit, they are designed in such a
manner as to enable them to develop their full power of 620 k.w. at
4,000 volts as single-phase machines. In that case, with a non-inductive
load, the drop amounts to 9*1 per cent. Each of these generators is
separately excited by a four-pole exciter of 12 k.w. at 60 volts, the
armature of which is mounted on the main shaft. These direct-current
machines for exciting the three-phase generators receive in their turn
current for exciting their fields from two other direct-current machines
separately driven by turbines each 20 H.P., developing 14 k.w. at 125
volts at 850 revolutions per minute. The reason for this indirect way
of exciting is that the fluctuations in the speed of the main turbines,
due to the variation of the load on the generators, have less influence
on the pressure than if the field of the exciter was to decrease simul-
taneously with the speed of the generators and exciters. The field
regulation of the generators can be effected either separately or in two
groups or else all together, as desired. It is done entirely by means of
the secondary exciting circuit. Any alteration of the resistance in the
circuit of the secondary exciting machine is avoided by suitably
arranged rheostats,, which are switched on automatically during the
regulation, so that in any case these secondary exciting machines
always remain under constant load both during the regulation itself
and after switching in and out of the fields of any number of genera-
tors. 'As the current to be supplied by these secondary exciters does
not exceed six amperes, it was possible to arrange the rheostats very
neatly. The shunt-breaking resistance of the exciter switches was
arranged with an adjustable air-gap. The terminals of the generators
arc coupled up by small cables, arranged in small tunnels which are
quite accessible to the main switchboard, which is of the usual Swiss
make with a facing of white marble.

The main switchboard itself is in another room adjoining the
main building, 50 ft. by 15 ft., and is supported from the ground on
rolled-steel joists about 9 ft. 6 in. up. On this board, which fronts the
engine-room, are fixed all the necessary instruments and regulating
resistance wheels, switch levers, etc. At the back, in the other room,
under the floor, are arranged the 'bus-bars to which arc run the
generator cables. There are no 'bus-bars fixed to the switchboard
itself, and all conductors on any panel may be disconnected from the
'bus-bars by removing the links at floor-level. The 'bus-bars are

858 RISELEY: SOME NOTES ON CONTINENTAL [Newcasde,

•divided into two sections, so that it is possible to operate two circuits,
which are called steady and unsteady. The two sets of 'bus-bars are
arranged in a circular fashion^ so that either can be closed or open at
certain points. In this way it is possible to work the two circuits either
separately or together. At the time of my visit the bars were divided,
the unsteady service supplying current to the Burgdorf-Thun line, the
other suppl)dng all the rest. Arrangements have been made to enable
the two circuits to be worked together in case of any breakdown of
apparatus. The central panel of the switchboard contains a switch
lever for connecting the two 'bus-bar systems. The regulation of the
two separate services (which was extremely arduous, due to the great
head of water, and being unable to govern well) is affected according
td the requirements, as shown by the two 'bus-bar voltmeters arranged
at each end of the switchboard. In order to enable the generators to
be used in any desired combination for the joint or separate working
of the two services, the driving devices for the regulating rheostats are
* capable of being coupled up all together or in two groups as desired,
so that they can be operated by the two large hand-wheels directly
under the voltmeters. Adjoining the generator panels at each end is a
panel for connecting the two sets of 'bus-bars with transformers which
transform the pressure from 4,000 volts up to 16,000 volts for trans-
mission. Places in the immediate neighbourhood are supplied direct
from the 'bus-bars at 4,000 volts.

Under the switch-room is a transformer-room, in which is an over-
head crane, which can be travelled into a repair shop*. The trans-
formers on being taken out of the repair shop are lifted on to a bogie caJt on
rails, and are transported along rails laid across the whole transformer-
room to their place. They are slid off the bogies on to rolled-steel
joists sunk into the concrete, just projecting about J in., and thus it is
very easy to change the transformers in case of any breakdown. They
do all their transformer repairs at this station. .At each side of the
transformer-room there is space for nine transformers. Up to the
present only eight have been installed. They are single-phase trans-
formers immersed in oil, and water cooled, capacity of 300 k.w., the
efficiency being 98 per cent., star connected. Four of these trans-
formers are on the steady circuit, two of which are devoted entirely
for lighting and are operated in parallel, being connected to the single-
phase circuits. The other two are used for power. The other 'bus-bar
system, called unsteady, has three transformers coupled up with a
fourth in reserve, which is capable of being switched into any desired
phase by means of special switches in the primary and secondary
circuits.

All conductors, including the high-tension conductors from the
terminals of the transformers, are taken through the ceiling into the
transformer switch-room situated above. Insulation through the floor
is ensured by very thick glass tubes about 20 in. long. In the trans-
former switch-room are arranged in a clear and easily accessible
manner all the switch levers and instruments for the primary and
secondary circuits both for the transformers and transmission line.
The 'bus-bars of the two services are each led along the longitudinal

1903.] POWER-HOUSE EQUIPMENT. 869

side of the room, and the switch apparatus for the primary circuit of the
two groups of transformers is accordingly arranged at both sides of the
room, being separated in accordance with the two services. Each
transformer has a switch panel of its own, containing oil-break switch,
ammeter, and fuses. Opposite these, in the centre of the room,
are arranged 'bars and switches for the high-tension circuit of the
transformer. The high-tension fuses used on these consist of
aluminium fuses in the usual Brown handle. The latter are
surrounded on four sides with slate division plates, the front being
protected by a removable grating. All the switches and instruments
of the 4,ooo-volt circuit as well as the i6,ooo-volt circuit are arranged,
not on switchboards, but on light, open steel structures, of course
everything being well supported on Insulators. From the high-tension
'bus-bars of the two banks of transformers are run two sets of con-
ductors (bare) to the distributing board for the overhead line, the
front of which is a marble panel arranged on a raised platform on
the north side of the room. The latter 'bus-bars are also divided into
two sets, which make another ring circuit same as before, or may be
separated from each other at different places, so that the separate
feeders may be switched on to any of the two services. Each panel
contains fuses, an ammeter in each phase, as well as a three-pole
oil-break switch. All switches are mounted well above the panels in
order to avoid any arc, if any should be formed jumping across from
the bars underneath. The switches are all worked by levers, either by
means of a chain or rope. From the feeder 'bus-bars wires are led
into the open through holes in vertical marble slab, being also insulated
by very thick glass tubes. Altogether there are 14 cables led away
by the overhead line. Three branch away immediately on leaving the
power-house, and are for local consumers in the immediate neighbour-
hood ; these are at 4,000 volts. The remainder, being \ in. diameter,
carry current at 16,000 volts, and are carried as far as Thun on iron
lattice columns. The insulators are secured in two groups by means of
bolts and lock nuts to vertical wooden supports (creosoted), secured to
the iron frames at the top of post at a height varying from 28 ft. 6 in.
to 39 ft. 6 in.

Three lines are utilised in working the Burgdorf-Thun line. Three
go to Burgdorf ; five to Berne, two single-phase and three three-phase.
The iron posts, which are fixed in blocks of concrete in the lake itself,
are all connected with the earth by a wire passing under the high-
tension line. At certain places, especially at curves and railway
crossings, the construction is a little heavier. The insulators are of
a special type, 6^ in. long, with a double petticoat 4^ in. deep. This
line ends at Thun in a distributing tower, and from this point the
lines are carried on timber poles from 25 ft. to 46 ft. in height. As said
before, five of these lines go to Berne ; of the remainder, three go to
transformer stations for the railway and the other three to Burgdorf,
all supported on poles. In the event of a low-tension wire snapping
or springing up against the high-tension lines, all chance of danger is
obviated by the fact that the wire would come in contact with the
earth-wire first.

860 RISELEY: SOME NOTES OX CONTINENTAL [Newcastle,

The distribution in Berne takes place from a closed-ring circuit
formed by the five wires, and surrounds the whole town, to which
circuits are tapped on four transformer stations. These sub-stations
are arranged in double-storey ed buildings of about 265 square feet
area, and consist of a front room, which is utilised as an erecting
shop and provided with a travelling crane. The transformer-room
adjoins this, and the switch-room is overhead. There are four trans-
formers in each station, although the buildings are designed to take
seven, each having a capacity of 50 k.w., and are immersed in oil and
water cooled. The leads to the transformers come from the switch-
room overhead, along whose walls is arranged all the switching
apparatus, high-tension one side, low-tension the other. The switches,
fuses, ammeters, and lightning arresters are arranged on identically the
same lines as at the central station. The ring circuit can be discon-
nected from the transformers by means of two special switches
arranged close to the spot where the high-tension lines enter the
building. These switches are operated by long levers outside the
building, so that the portion of the ring circuit situated between two
substations may be deprived of the current without necessitating
entering the transformer stations and interrupting the working.
The pressure is reduced by transformers to 3,000 volts, and the current
passes from the secondary 'bus- bars to the underground cables
supplying the town. Inside the town the pressure is reduced to 250
volts for driving motors, and to 125 volts for single- phase lighting.
At Burgdorf, which is the second distribution centre, the voltage is
reduced by two transformer stations from 16,000 volts to 500, and the
power is used for driving large motor§. For working the smaller
motors, as well as for lighting purposes, continuous current is used.
This is obtained by two motor-generators which convert 500 volts
three-phase to 150 direct current. This energy is distributed by a three-
wire system and by two batteries of 840 ampere-hours capacity.

The operation of this installation presents, of course, special
difficulties, on account of its being necessary not only to supply
a large amount of current for lighting and power purposes only,
but also at the same time to provide for extremely large variations
in the power required for the railway traffic. In order to prevent
these fluctuations from affecting the remainder of the system, the
installation is arranged for working two entirely different services. A
good idea of the variation may be gained from the fact that it is by no
means exceptional for the railway to suddenly take for a more or less
considerable period as much as 1,200 H.P. To sum up, the special
points to my mind worthy of attention are that the 'bus-bars are
arranged exactly as a ring main in a boiler-house. Four of the
generators may be switched into one or the other feeder circuits as
desired by means of the ordinary switches. The various duplicate
'bus-bars on the generator switchboard in the transformer switch-room,
as well as on the feeder switchboards, are all arranged as ring circuits,
which, by removing or closing linking devices, can at any moment be
divided into any desired section, so that in this way all kinds of
combinations in working can be readily effected. The transformers

19(^.] POWER-HOUSE EQUIPMENT. 861

used are all single-phase, which allow in case of any of them getting
out of order to switch in at once a reserve transformer into the
corresponding phase. These single-phase transformers enable the
output of one phase to be increased by switching in further trans-
formers, which, as in this case, where the whole lighting circuit is
connected to one phase, is of special importance for the regularity of
the supply. Finally, the whole line is arranged, especially as regards
switchboards, with ample room everywhere, so that the extra high
pressure does not in any way interfere with the reliability of the system.

Valtellixa Line.

A short account of the Lecco-Colico railway may be of interest. I
found that although the Une was equipped as far as Lecco, starting
from Colico, that at that time there was no regular service running,
as only experimental cars had been run up to the time of my visit.
As is well known, the system is three-phase, with the overhead line
at a potential of 3,000 volts. The power is primarily generated at
Morbegno at a pressure of .18,000 to 20,000 volts direct. The plant
consists of three 2,000-H.P. generators running at 150 revolutions per
minute, 15 cycles, having a capacity of 1,300 k.w. ; exciters on turbine
shaft end ; voltage of exciters, 45. The machines are extremely well
ventilated and the windings on the machine spaced widely apart.

There are practically two sets of main high-tension 'bus-bars, and each
generator feeds into both through high-tension circuit breakers. Each
generator has one ammeter, wattmeter, and synchronising voltmeter and
lamp ; the pressure on the instruments is reduced by static transformers.
There are six lightning arresters, three to each set of bars, one arrester
being placed in each phase. The high-tension switches are identical
with the old Siemens lightning arresters : on opening the contacts the
arc forms between the nearest points of the horns and travels upwards,
due to the heated air, until it breaks. The current is conveyed from
the power-house by means of a transmission line to nine sub-stations
situated at the side of the track ; at these sub-stations the pressure is
reduced to 3,000 volts, which is carried on the overhead Hne. . With
one exception only, the sub-stations each contain one three-phase static
transformer of 300 k.w. normal rating, but capable of working for a
short time up to 900 k.w. One of these nine sub-stations contains two
such transformers. The cooling apparatus consists of a small blower
driven by an induction motor. The transformer sub-stations are
separate stone buildings alongside the railway stations, the transformers
being placed in a specially locked room, which is inaccessible to the
ordinary railway officials.

The transmission line, at 18,000 volts, runs parallel to the railway a
short distance away, but, of course, does not run through the tunnels,
of which there are a great number, but over the mountains. Nor
does it run through the stations, but at some distance from them.
Lightning arresters are placed on the primary line every three miles,
and on the secondary every ij miles. The secondary leads are
spaced 60 cm. apart, the primary at 87 cm, The secondary is an

862 RISELEY : SOME NOTES ON CONTINENTAL [Newcastle,

ordinary trolley wire, and the primary varies in diameter according
to the amount of current it has to carry. A separate span wire is
always used for each phase, and double insulated. Of course, the
rails are used as a return. All the rails are bonded with ordinary
trolley wire, only instead of the pin being solid it is hollow, and
collapses when being driven in, and in no case has trouble been
experienced through defective contact. Originally the railway com-
pany insisted on protected bonds being used, and these were tucked
away at the back of the fishplates ; but after two years it was found
that lo per cent, of these had got broken, so the plan was abandoned,
and the bonds put in an unprotected manner, and just buried in
the ballast. Since doing this no further trouble has been experienced.
The track is also cross-bonded at about every 300 yards.

On making a trip on the track, I found that the acceleration was
extremely even, there being no jolting whatever. The starting
resistances on the car consist of water in a tank with fixed plates, the
level of the water being raised or lowered by compressed air, which is
also used for the Westinghouse brake, the whole apparatus being
worked by a small valve in the driver's compartment ; the time
occupied to take out all the resistance varying from 16 to 60 seconds,
depending on the weight of the train, gradient, etc. The air-com-
pressor is driven by a small motor with an automatic switch, which
stops the motor when there is sufficient pressure in the tanks. The
trains take up to 90 amperes at 3,000 volts to start up, this being the
maximum, and from experiments a train on a gradient of 17 in 1,000,
with a draw-bar pull of four tons, got up to speed in 37 seconds.
There are loop lines on the overhead line through the stations
which are made dead as soon as the train comes to a standstill ; also
the trolley boom is lowered, this being also operated by compressed
air, and in the event of a car standing for a long time, there is a
small hand-pump to get sufficient air pressure to raise the trolley to
get current in order to start up the motor for the air-compressor. The
air-compressor also works the whistle.

There are two ways of lighting the trains, either with accumulators
or else by means of transformers and lamps with three filaments at
100 volts 15 cycles. A small 8-k.w. transformer supplies current for
the lamps, motor, compressor, and heating. The flickering of the
lamps was hardly perceptible, more especially those behind ground
glass. The same system of lighting was employed at the stations.
The main switch on the car was operated also by compressed air, and
there was an interlocking arrangement, by means of which it was
impossible to get at the switch if the trolley was up, and, of course,
impossible to put the trolley up if the switch was open. The trolley
was of novel construction, consisting of a copper pipe running on roller
bearings, and the whole supported on a wooden shaft. These trolleys
have run 30,000 miles without being renewed. The cars are mounted
on two four-wheeled bogies, each of which has one primary and one
secondary motor mounted direct on the axles. They weigh about
50 tons, and can seat 56 passengers. The locomotive gave a draw-bar
pull of 10,000 lb. at 19 miles per hour. The body of the locomotive is

1903.] - POWEK-HOUSE EQUIPMENT. 863

mounted on two four-wheel trucks. Upon each of the four axles a
motor is directly mounted, no gearing being used.

All motors are primary, and s|)eed regulation is obtained by using
either one, two, three, or all motors to suit the conditions. The rotor
shaft, which is hollow, is connected to the car axle by a flexible
coupling. The coupling is balanced by counterweights, by this means,
although running in fixed bearings can drive the wheel, at the same
time allowing the wheel and axle to rise and fall with the inequalities
of the road, only /jths clearance being allowed on the rotor. The
average speed is fairly high, as the acceleration is very rapid, although
the maximum speed is not excessive, it only being 60 k.m. per hour.
They were able to coast above synchronous speed down hill and they
coasted below synchronous speed on the flat. The two most efficient
speeds were 30 k.m. and 60 k.m. per hour. The whole scheme, in-
cluding power-house, water power, and canals for same, work out at
;£4,5oo per mile.

On carefully considering the design of the foregoing power-houses
and equipment, it seems to me that two things have especially been
aimed at — viz., simplicity of design, and a duplicate arrangement of
all gear as far as possible. In getting out designs for new power-
houses engineers generally consider, in regard to the relative capacity
of engines and generators, that the most economical load for the
engine shall be that of the maximum load of the generator, and they
arrange that, by lengthening the cut-off on the engine, the generators
shall be capable of being greatly overloaded without reducing the speed
of the engine. In the new power schemes that are before us to-day,
where it is absolutely necessary to keep up an uninterrupted supply,
it is necessary to take all precautions possible to keep the station 'bus-
bars alive at all times and at all costs, notwithstanding any local
disturbance which may be taking place outside the control of the
power-house. The general source of trouble is fuses, more especially
now that much heavier feeders are in use than formerly, so that some-
times when a feeder is shorted it causes an immense amount of trouble
by fuses not blowing at the proper time, more especially if the fuses
on a system are of different design ; also, fuses do not always clear
themselves and thus blow the generator fuses, so that endless trouble
is caused. By making all the steam plant identical and of sufficiently
small capacity, so that in case of a heavy overload it will slow down,
all fuses and automatic circuit-breaking devices on the generator panels
may be avoided. In the event of a short occurring on a long-distance
high -voltage transmission line, the fault would almost immediately clear
itself ; if not, the engineer in charge will probably notice a different hum
in the machines, and will probably have noticed one particular feeder
taking an abnormal current, or else that the speed has dropped, and
will immediately open the faulty feeder. In case of a continued short-
circuit, the lower voltage limits the power which can flow through a
fault. By this system any interruption to supply would probably be
of very much shorter duration than if fuses are to be replaced and the
automatic circuit-breakers closed, after a general opening of all these
devices. Of course, there is the risk of all the motor-generators and

864

RISELEY: SOME NOTES ON CONTINENTAL [Newcastle.

rotary converters dropping out of step, but I have known cases where
motor-generators have kept in step even with a variation of 20 per cent,
in the speed of the generating plant.

Mr. Stewart. Mr. ANDREW STEWART {communicatcd) : The first point which
caught my eye as I read Mr. Riseley's paper was the amount of plant
in the Kander Power-house, some 3,720 k.w. on an area of 4,080
square feet, or i*i square foot per kilowatt. This is a figure which,
although it has been improved by some of the high-pressure water-
power plants employing Pelton wheels on the Pacific coast, is never-
theless a good example of a Continental water-power plant wth a
medium fall. Having beside me a few figures for power-houses in
New York and Berhn, I give them below, with the relative position of
the boilers and the type of engines, all of which influence the area
required per kilowatt.

it s

u- O C

y u o

c
as

O JS

o u

P-^

' 8

i 1?^

' Hl^

1 «

j»;

x:
c

o
o

^ s

1903.] POWER-HOUSE EQUIPMENT: DISCUSSION. 866

Oberspee and Moabit will have all extension units of 6,000 H.P., and Mr. sicwart.
figures given are based on ultimate capacity of station when buildings
are full.

The German H.P. is i| per cent, smaller than the English, but that
does not materially alter the figures. On my visit to the Berlin stations
some months ago neither had reached its full capacity, but there was
no evidence in either case of economical tendencies as to ground space,
chiefly because ground was very cheap, each station being located
some miles from the centre of the city. The figures probably repre-
sent the extremes of large power-station design, as even in London the
area per kilowatt of any of the stations is not much less than that of
the Metropolitan Station, New York, although in conversation with the
engineer of one of tRc new underground railways for London I learned
that with Parsons turbine units it was hoped to get the ground space
in one power-station down to one square foot for each kilowatt installed.

Mr. Risele/s reference to the transformation of three-phase cur-
rents by three single-phase transformers is also interesting, instead of
the more usual Continental plan of employing three-core transformers
for this purpose. The e^e with which another single-phase transformer
may be switched in to replace any one of the three should it happen
to break down, is not sufficient to justify the extra capital expenditure,
which may be 10 to 20 per cent., depending upon the size. In addi-
tion to this, I note that a good proportion of the power at Berne is
used as single-phase, where of course there will be some tendency
towards unbalancing. This tendency can best be checked, tf not quite
suppressed, by the use of three-core transformers, the interaction of
the three phases being sufficient for this purpose. If Mr. Riseley has
heard this point raised at Berne, perhaps he can throw some light on it.

Another interesting point is the Lecco-Colico line, where it appears
that 15-cycle 3-phase currents are employed throughout. It would be
interesting to know what considerations led to the choice of this low
periodicity ; certainly the motors and transforming apparatus would
cost a good deal more than with a higher periodicity. One considera-
tion which appears to justify this low periodicity would be the greater
apparent resistance of the rails with currents of a higher periodicity. If
the rails have a large section, this would probably become a matter of
considerable importance, but it is doubtful if it was the reason for the
adoption of a periodicity of 15 cycles. Perhaps it may have been due
to mounting the motors direct on the axles, and using driving-wheels
of small diameter ; this, with a small number of stator poles, say four,
would correspond to the higher speed mentioned by Mr. Riseley, viz.,
60 kilometres per hour, but this would involve wheels approximately
30 inches diameter, and it is improbable that the motors could be
mounted directly on the axle in the space available. There must of
course be some good reason for such a departure from recognised
practice. Another point is the statement that each bogie on the cars
has two motors, one primary and one secondary ; this would lead one
to suppose that they are arranged permanently in cascade, which seems
unhkely, unless when running at 30 kilometres per hour, while the next
paragraph says "all motors are primary." It is difficult to reconcile

866

RISELEY: SOME NOTES ON CONTINENTAL fNewcasUc,

Mr. Stewart thesc two Statements, as they indicate directly opposite practice, and I
shouid like to have Mr. Riseley's views.

Mr. Mr. W. B. WooDHOUSE was interested in comparing the methods

adopted for the protection of the system in the stations described with
those used in other countries. He noted that the use of fuses was
general, but he was surprised to find aluminium fuses still in use.
Aluminium had been used because its specific heat was large, and it
was possible, by carefully proportioning the cooling surface, to make
such a fuse act as a time-limit cut-out, but the difficulty of making a
good connection had caused most engineers to abandon its use in
favour of tin, to which copper connecting strips were sweated.
Modern practice in this country and in America^ was to abandon
fuses altogether in favour of automatic oil-break switches ; feeders
were protected by overload time-limit switches at the generating end,
and overload and non-return power switches at the receiving end. He
did not consider automatic switches or fuses necessary on generators,
an oil-break switch being sufficient, if properly enclosed in an iron box ;
he quoted a case of such a switch repeatedly breaking 12,000 kw. at
45,000 volts without damage. With regard to a suggestion of Mr.
Riseley's, that small engines should be used which would pull up on a
short-circuit, the speaker could not agree with this rather primitive
method, as all the synchronous sub-station machinery would undoubtedly
fall out of step. An automatic switch was the proper thing to use.

Mr. stoney. Mr. G. G^^Stoney Said he was much indebted to Mr. Riseley for his

paper. It enabled us to compare our systems with those of our Conti-
nental competitors.

When he was over in Germany the thing which struck him most
was that the capital expenditure was excessive, especially for buildings.
Take two modern stations. The style of buildings would never be
countenanced in this country, and the space occupied by the plant was
excessive. It was ij square feet per kilowatt, without taking into
account switch-room. If the switch-room were taken into considera-
tion it would work out at 1} square feet. The space used was ij
at Neptune Bank. In one station £130 per year was spent on
washing floors. The result of this excessive expenditure would be
disastrous at some future time. The charge for current was higher
than it was in England, being as high as 7d. and 8d., whilst in New-
castle it was 4id.

His opinion was that for real sound work England was far ahead of
the Continent. He quite agreed with Mr. Woodhouse that fuses were
a great nuisance. He would be inclined to do away with fuses,
especially main fuses, on machines. Fuses of aluminium in china
handles, of the Brown- Bo veri type, seemed to work fairly well.

Mr. vescy Mr. C. S. Vesey Brown Said that one envied the French, Swiss, and

iJrown. Italians in the possession of their magnificent waterfalls, and unfor-

tunately the conditions in England were so different that manufacturers
and others connected with central stations were obliged to use steam to
compete with their Continental neighbours. He did not know of any
other water-power station than that of Reinfelden, in Germany, where
most of the stations were steam-driven.

1903.] POWER-HOUSE EQUIPMENT: DISCUSSION. 867

In reference to the author's remarks on fuses, he had found that the Mr. Vescy
general rule on the Continent was to use pure silver, which was far ^°^^'
more reliable and certain to go at the proper current density. For his
part he had given up the use of fuses for large currents except where it
was required to disconnect any leads, and preferred to use instead a
good maximum automatic cut-out with a carbon break attached.

At his first visit to the Cologne Station in 1 891. he found that the
authorities were most particular as regards periodicity and pressure,
and, in fact, were so successful as to be able to run about two dozen
clocks in synchronism with the generating plant, and these clocks were
set once a week.

There were many opinions as to the question of using storage bat-
teries, and they had certainly stood the test of time at Dresden and
Dusseldorf, but the tendency being all in favour of three-phase genera-
tion had to a certain extent displaced the storage battery. There was
certainly the point as to constancy of pressure which was more par-
ticularly brought to the front when Nernst lamps were used on the
circuits, and in his opinion the use of the Nernst lamp required that the
pressure should not vary beyond the very narrowest limits from the
standard pressure. It seemed a pity that in the town in which they
were at the present moment, that the use of the Nernst lamp had to a
very great extent been killed by the great variations in pressure to
which the distributing system was subjected, and he thought that this
might be remedied by the use of storage batteries.

On the Continent the price of supply was as a rule higher than in
this country, but this was due to the very lavish manner in which the
buildings had been laid out, and as the upkeep was heavy, so the con-
sumer had to pay more for his supply. The Continental proprietors
were satisfied with a slightly smaller return on the capital put into the
stations, for as a rule, where the stations were not owned by the local
authority, they were owned by manufacturing companies, who put a
good price on the value of their plant at the commencement. In some
cases the tax to be paid by the concessionaire to the local authority
t>efore the shareholders received anything was 6 per cent, on the
capital employed ; in others it was as high as id. per unit.

Referring again to the use of storage batteries to steady the pres-
sure, he was informed at Essen that the town authorities imposed a fine
for irregularity of pressure and failure to supply, but that up to the
present no fines had been imposed in consequence of any failures, etc.
In his opinion the German stations were much better finished than
the French and were generally cleaner, though they were both a great
deal ahead of this country in this respect.

Mr. C. TuRNBULL said he was interested in Mr. Riseley's remarks on Mr.
cellular switchboards. People were often led to believe that the only '''"*'"^""'
fault of this type of board was its high cost, although the board certainly
appeared rather inaccessible. He was pleased to hear the criticism of
one who had used them.

With regard to running dynamos without fuses, it was to be observed^
that an engine's power went off rapidly as soon as it slowed down, and
he believed it well worth while — speaking from experience — to have

666 RISELEY: SOME NOTES ON CONTINENTAL [Newcastle,

Mr.

Turnbull.

Mr. SneU.

Mr. Clothier

dynamos large enough to pull the engine up without damage to the
dynamo.

Mr. J. F. C. Snell said he would like Mr. Riseley to tell them
whether he found the oil-break switch more in use than the air-break
switch. He understood that the Continental practice was to use the
horn-switch. He was, however, sufficiently English to have adopted
oil switches in connection with his three-phase plant.

It occurred to him that the money spent on buildings — particularly
on the engine rooms— on the Continent was very excessive indeed,
owing to the fact that they used slow-speed engines which covered a
great deal of room. This was, of course, done with an object, the cost
of coal being so great that they were obliged to adopt every possible
means in their power to reduce the consumption per unit sold. The
sub-stations of Berlin struck him particularly as being lavish. The
walls in some cases were 36 inches in thickness, and the floors were
most heavily made with glazed brick facings. Although land was dear,
the fact of putting accumulators on the first floor when they could have
been put in the basement seemed waste of money. While he thought
that their engine rooms looked better, their boiler-house equipment
was wanting when coyipared with English practice. English central
station engineers would be ashamed of the usual Continental boiler
house. The arrangement of piping also seemed to be bad. Sup-
posing they had a superheat of 250° at the boilers a good deal must
be wasted before reaching the engines, owing* to the long pipes
employed.

It was interesting to hear the remarks about the single-phase trans-
formers. He found three-core much cheaper than three single-phase to
install. None of the previous speakers touched on the question of
railways. The Institution had wisely arranged a trip to Italy this year.
He hoped the experiments on railway equipment being made in Italy
would teach us a great deal and have the effect of awakening our
English engineers.

Mr. H. W. Clothier said he was not so favourably impressed with
the design of Continental switchboards as Mr. Riseley. When he
visited stations containing such switchboards he found that the backs
were not open for inspection to visitors, and he instanced one place
where he learnt" that two men had been electrocuted behind the board.
He alluded to the comments on British switch-gears, and thought that
an unfair comparison had been made. The cellular switch-gears at
present in use in this country were designed for pressures of about
5,000 volts and under, whereas the Continental system taken as an
ideal was working at 13,500 volts ; when the demand for higher pres-
sures arose in this country we should produce designs to excel those
seen hitherto by the author. He did not attribute so much importance
to the duplication of 'bus-bars which introduced complication and
chances of error. He drew attention to an error in one of the diagrams
which was a good example of the difficulties due to too much com-
plication ; if the draughtsman could so easily err, what was to be
expected of the operator?

Mr. Riseley had said that on the boards to be seen on the Continent,

IdOd.] POWER-HOtrsE EQUIPMENT: DISCUSSION. 869

such as that at Paderno, there was " always another way round, every- Mr. ciothier.
thing being in duplicate, but he (Mr. Clothier) thought that an examina-
tion of the diagrams would show that such was not exactly the case.
The 'bus-bars were in duplicate, but that was all. He maintained that
apart from the complications involved (which were common to any
type) there was no difficulty in obtaining by this means " another way
round " on the British cellular gear ; as a matter of fact he could mention
many cases in this country where duplicate and even triplicate 'bus*bars
were in use.

He said that flare switches for alternating-current systems were iast
dying out, because of the high voltage oscillation set up by the arc. In
the light of our experience and the expert opinions of this country and
in America, no one would think of installing switches of the same type
as those in use on the Valtellina line.

He was entirely in accord with the author in his practical opinion
as to dispensing with fuses on the generator circuits, fuses there were
more often than not a nuisance ; they were wanted on the feeders, and
he thought reverse current indicators on each machine circuit were
used to advantage.

Speaking of the general design of British switch-gears, he admitted
that there was ostensibly much to be done before they could be con-
sidered perfect for extr^f high voltages ; but in arriving at finality in
design, if that were possible, we should take into account the enviable
record of no fatal accidents on the Ferranti cellular switch-gear during
all the years it had been extensively used on high-tension supply
systems.

Mr. J. H. Holmes said he had the pleasure of visiting Kander Mr. Hoimts.
Power Station with some members of the Institution.

The thing that struck him most was the great difficulty they had
in regulating and governing their turbines. It seemed impossible to
design an automatic governor which would be of any use. When he
was there he had noticed the man at the hand- wheel, and he was
interested to learn that he was still at it.

Mr. H. L. RisELEY, in reply, said that Mr. Stewart's figures of area Mr. Riscicy.
of ground per kilowatt installed were very interesting, and he was sorry
he could not add to the list. The sole idea of using single-phase trans-
formers was, he was informed, for the convenience of changing over
in case a transformer got damaged. Valtellina Line, — He presumed
that the reason of choosing a periodicity of 15 cycles per second
was the wish to mount the motors direct on the axles. The wheels,
instead of being 30 inches, were 3*84 feet in diameter on the motor cars,
whereas on the locos, they were 55 inches in diameter. The motors
were mounted directly on the axles in a very interesting manner. The
gear consisted of a very neat parallel-link connection between the
driving hollow rotor shaft and the wheels. Each pair of wheels was
keyed to the shaft, of which the diameter was 4^ inches less than the
inside bore of the hollow shaft, and the Unk gear compelled the two to
rotate accurately together while giving complete freedom to the wheel-
shaft to rise and fall with the axle boxes between the horn plates
without any vertical motion of the rotor, stator or motor as a whole.

870 RISELEY : SOME NOTES ON CONTINENTAL [Newcastle,

Mr. Riadcy The whole weight of the motor was borne on springs ; the bearings of
the rotor shaft were fixed in the casing of the stjitor. The wheel was
driven by pure torque, that is to say, by two equal and opposite forces
producing no reactive resultant pressure in the bearings in which the
rotor ran. The whole load, including the weight of the motor, was
carried at the axle box.

As regards the primary and secondary motors, each motor car was
fitted with two primary and two secondary motors, but on the locos, all
four motors were primary, and speed regulation was obtained by using
either one, two, or three, or all motors, to suit conditions. On the
bogie cars each truck carried two motors, one on each axle. These
were used in cascade up to half-speed, and also in slowing down from
full-speed to half-speed. In accelerating from half- to full-speed, and
in running at full-speed, one of each of the pair of motors was cut out
and was running idle. Of course, in cascade-working during the first
period of acceleration, the resistance was placed in the rotor circuit of
the secondary motor, in the stator of which the voltage did not rise
above 300, this being derived from the rotor of the primary motor,
which current was drawn off slip-rings. The Controller had only
three positions : (i) half-speed ; (2) mid position, when the resistance was
cut out and the primary rotor circuit was open, and (3) full-speed,
for acceleration from half -speed to full-speed.

Mr. Woodhouse mentioned aluminium fuses and seemed to have the
idea of making fuse contacts of aluminium strip. Messrs. Parsons
& Co. used special blocks for soldering aluminium strip.

As regards the time-limit circuit-breaker he did not see any in
operation, though he understood that they were experimenting in
Newcastle with them and that they were working fairly satisfactorily.

Regarding the last paragraph of the paper his idea was, supposing
you get a number of 100 k.w. generators running in parallel with identical
engines of the same rated power. In that case, should any overload
occur, all the engines would slow down together, instead of a more
powerful engine trying to take all the load and thus upsetting the
parallel running of the station. He only offered this as a suggestion.

In reference to Mr. Stoney*s remarks, no doubt some of the
Continental stations were got up most expensively, especially that
of the Schuckert Corporation Station at Vienna. The work of clean-
ing the station was a big item ; in some cases it cost £2 per week to
keep the floor clean. He did not remember seeing a station in England
kept so clean as the Continental stations.

In regard to the point raised by Mr. Vesey Brown about the cheap-
ness of water-power abroad, the capital expenditure incurred in
applying water-power was enormous. In some cases they were
using steam plant, as the capital outlay in utilising the water was
almost prohibitive, and they found it better to have steam engines.

With reference to sub-stations being well equipped, he did not
know that it did not pay to put in all the automatic devices you
can. It certainly saved labour.

Turning to Mr. Clothier's remarks : he did not think there was any-
thing in the paper about Ferranti switchboards. There was more than

1903.] POWER-HOUSE EQUIPMENT: DISCUSSION. 871

one type of switchboard called multicellular. There certainly were ^^' K^»*'«y
several points on the Ferranti switchboard which could be improved.
Accidents with it were not unknown. It certainly was an advantage to
be able to get behind the board, which it was impossible to do with the
Ferranti board. He agreed with Mr. Holmes that the governing
at Kander was extremely bad. With a large volume of water rushing
down under a high pressure, it was evident that the governing could
not be very uniform.

Vol. 32. 57

872 TAYLOR: NETWORK TESTS, [Birmingham.

BIRMINGHAM LOCAL SECTION.

NETWORK TESTS, AND STATION EARTHING.
By A. M. Taylor, Member.

{Paper read before the Section^ February 25<i903.)

The object of the present paper is, primarily, to describe a new
station test, for application under working conditions and on systems
where the middle wire is permanently earthed ; but as the utility of the
said tests— or, indeed, any known test — depends considerably upon the
method of earthing adopted, it has seemed desirable to add a few notes
on this subject also.

SECTION I.
Descriptive of Test, and Explanatory Diagram.

Referring to the simple diagram of circuits, Fig. 3, let E represent
part of the earth circuit, and P, M, N the positive, middle, and negative
leaks respectively.

D, D are the dynamos or steam balancers at the station. AA is
the Board of Trade Recording Ammeter, reading from o to 100 amperes,
the neutral being earthed through a resistance of 2*3 ohms, as shown.

For the present, consider only the currents P, M, N, and let the
leak P be of lower resistance than N, so that the potential of the earth
tends towards that of the positive pole.

Consider also, for the moment, that the resistance of the earth is
negligible, and hence that the earth potentials at the leak and at the
station are the same.

We can represent this state of things by the small diagram on the
right-hand top corner of Fig. i.

Fig. I represents, to scale, the changes which take place in the values
of N, M, P ; and AA, if we can imagine the potential of the earth
pulled, by some external means, through every value from extreme
positive to extreme negative.

To enable this diagram to be better understood, the author has
dissected that part of it which relates to the P and N leaks ; and the
two triangles, the ordinates of which represent at any moment the actual
values of the currents P and N, are shown separately in Fig. 2 (con-
sider only the full lines). The dotted lines of Fig. 2 are intended to
help to the better understanding of Fig. 14 (see Appendix, Note i).

The differential leak is given us by the ordinates drawn between the
base line and the hne AB, Fig. i, which for shortness we will call the
P-N line : see also Fig. 2. The point at which this line crosses the hori-

1903. J

AND STATION EARTHING.

873

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-IVIJLN3J.0dJ0 aNoS

r.\^i^'

..yli! |. ... sf,

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i '''^-3? •'•' -"'

a
8

•a

'•3

«va sng 3Allvo3n

jonVLLN3XOd ^o 3Nn

874

TAYLOR : NETWORK TESTS,

[Birmingham,

zontal gives us the potential of the earth when P = N, there being
assumed to be no neutral leak.

Next, introduce a neutral leak, indicated by the lengths of the ordi-
nates between AB and CD, and we see the effect in bringing the earth
potential nearer to that of the neutral 'bus-bar. The point of crossing
of CD with the base line is now at 60 volts.

Again, add a further line EF, representing by the ordinates between
it and the line CD the current in the B.O.T. connection (made through

rr^

1 v^

PosmvE •

MonCMTARY

! "V^

Fault

!-H Fault

r-.^'^^'.

oevcxx>Ps

^^^=^^:Cij^j/^N

Positive .

^v^^(^

N ^

(NOMMAO

^\.

^r^^v^>

r^^r^

^'^^

NCCWTVC

(fMKMAL*

NecATive

P^55^..

of^^.!^

Fig. 2.

2'3 ohms), and we have the new potential of earth, viz., 10 volts, where
EF crosses the base line. The ordinary B.O.T. reading is represented
by the ordinate AA, at V, volts, where V,/AA, = 2*3 ohms.

It will be obvious that no end of combinations of P, M, and N
will give the same B.O.T. reading AA,. Also that from the readings
AA, and V, (or from V, alone) we could, if only we knew A,, the differ-
ential leak when V ^ O, deduce the slopes of the lines EF and CD.
The slope of the latter line gives us the combined insulation resistance
of the three mains ; which is : —

F = cot. a =

1l
23

where a is the angle which CD makes with the horizontal.

To find the individual values of the leaks we must somehow separate
out the neutral leak from the others. Obviously, if we could only insert
an ammeter in the neutral leak and measure the little ordinate M,

Id03.]

AND StATlOK EARTHING.

d75

under V, volts, we could deduce the slope of the P-N line ; but,
unfortunately, this is impracticable, and would be only an approximation
in any case, as Mi is so small.

Referring, however, to Fig. 3, we see that by means of an artificial
fault at the station we might put M under any voltage we choose, and
measiu-e the increase or diminution of the current suppHed from the
station to the leak along the neutral feeders. Knowing the current

Pot mz .- A, . P,-<VfV>
. I :. AA.-p.-{n*n,)

Fig. 3.

produced under V3 volts, it is sufficiently correct to assume that under
V, volts we should have Vi/V^ of the current.

The author has successfully measured the increase or decrease of
the neutral current by interposing between the neutral 'bus- bar and the
neutral feeders a resistance, consisting of iron plates bolted together,
constructed to absorb about a couple of volts, and balancing against
this an accumulator cell with an ammeter in its circuit arranged to read
zero when the normal out-of-balance current of the station traverses the
resistance.

The difference in the reading when the neutral leak is under no

876 TAYLOR: NETWORK TESTS, [Birmingham,

E.M.F. and when it is under V- volts enables us to ascertain the
current through the neutral leak under V3 volts, whence we know M,.

It remains to explain how the reading A, is obtained. A reference
to Fig. 3 will show how it is picked up by the ammeter A at the
station through the switch and adjustable resistance. When V = 0,
then M = O, and A,= P-N.

Where the values of V, and Aa are both so small as to introduce
inaccuracy, it may be found desirable to take a reading A4 at V4 volts —
say 10 volts — to the left of zero (Fig. i), in addition to the reading A,
at zero voltage. Then —

F = cot. (

2-3

Fig. 4 shows the testing panel, as arranged by the author. The
switch shown at the top, when thrown over to the right-hand side,
introduces a central-zero ammeter AA into the B.O.T. circuit, which
gives us the normal B.O.T. ammeter reading AA, under the voltage
V, measured on the central-zero voltmeter shown.

The ammeter is unnecessary, since AA, can be calculated from
V„ but it saves reference to a table.

The second ammeter A is controlled by the two lower switches,
the upper of which puts the free end of the ammeter circuit on to
either ** outer " *bus-bar (through a fuse), and the lower on to the neutral
'bus-bar. The other end of the ammeter circuit, which contains an
adjustable resistance, is in permanent connection with earth. The
circuits are fused for 100 amperes.

To take the reading A,, all that is necessary is to close the up|>er
of the two lower switches on to the 'bus-bar remote from that
towards which the voltmeter reads and adjust the resistance slider till
V = O. Then on the ammeter A we observe the reading A,.

To measure the neutral leak, close the top switch on to the left-hand
side, thus putting the ammeter AA into the battery local circuit (see
Fig. 3), read the ammeter AA, the earth being at about the potential 6f
the middle 'bus-bar, take any suitable proportion of the resistance out
of the slider, and close the upper of the two lower switches on to either
"outer" stop. The increase or decrease in the reading of the ammeter
AA multiplied by a simple ratio— in the case the author has used the
ratio is 5/4 — gives the neutral leak M3, and the voltmeter measures the
volts V3 under which it is produced.

For localising a fault to any particular feeder, a 20-way slider is
arranged with an ammeter in such a way that the link connecting any
one of the neutral feeders to the distributing bar on the neutral feeder
panel can be opened, and the ammeter switched into its place.

If the last test be now repeated, the feeder on which the neutral fault
exists will give a very pronounced deflection amounting to perhaps 50
or 100 amperes if the fault is a bad one.

Suppose, now, that instead of a neutral fault we had a positive or
negative one. Then our test would have shown the neutral 'bus-
bar to be sound, and by the slope of our P-N line we should have

I90d.j

AND STATION EARTHING.

sil

known to which side to have looked for the fault. The next step would
be to cut some or all the resistance out of the slider, and to close the
upper of the two lower switches on to the right-hand stop (for a negative
fault), having previously graded the fuse for, say, loo amperes.

On inspecting the feeder ammeters on the faulty pole, the faulty
feeder will be at once seen.

To McuT^tAk. BJB Tb NKwrmAu.B.B.

L«AK "Tem-r R^mki-

(!) o--4J|

BOX I T

^-^ Lj

s.i.../tu. — — CEZID n f n crzjy i

Fig. 4.

I I

-^ t

SECTION II.
Reasons for a New Test.

The B.O.T. Recording Ammeter, for the reasons already given
under Section I., is not, as is well known, of any assistance in •gauging
the standard of insulation of our mains ; though it is, no doubt, of

878

TAYLOR: NETWORK TESTS,

[Birmingham,

considerable value as a recorder of any change in the state of the
insulation (except perhaps in that of the neutral) from day to day.
Hence some means of keeping the mains up to a standard is neces-
sary.

The four tests available were :— (fl) Fritch's Test ; (6) Frolich*s
Test; (c) A modification of Frolich's test by, and apparently due
to, Mr. F. C. Raphael ; {d) Mr. Alex. Russell's test.

The first three are described in Mr. Raphael's book on " Faults
in E. L. Mains," and they need not therefore be described here. Mr.
Russell's test (d) is described in the Journal of the Institution,
Vol. 30, No. 148.

With reference to these tests, the author would make the following
remarks : —

(a) Frisch's test is unavailable where the neutral is permanently
earthed, through a low resistance or otherwise.

{b) Frolich's test is also ruled out of court, because the resistance of
the ammeter circuit must be great in comparison with the insulation

ro-|

r-w

CotvietNCLo Animctcr ^KO Earttiinc Cohmkction
RAi»nACL*3 TtsrC

Fig. 5.

resistance of the network to be measured ; that is to say, if we arc
testing a network in a station supplying, perhaps, 50,000 60- watt
lamps, the joint insulation resistance of whose mains might measure,
say 20 ohms, we should need to insert an ammeter having in its circuit
a resistance of, perhaps, 200 ohms, between the neutral and the earth,
instead of the connection required by the Board of Trade.

(c) The modification of Frohch's test described by Mr. Raphael,
though no doubt more practicable than the others, still seemed to
be somewhat unsatisfactory.

In this test the neutral is temporarily connected to earth through an

1908.]

AND STATION EARTHING.

879

ammeter in series with a resistance about equal to that of the insulation
resistance of the network, and this circuit is then shunted by another
resistance of equal value.

The resistance to be inserted during the first half of the test would
then be, for the case above cited, about 20 ohms.

In the case, however, of a small system, the resistance to be inserted
might amount to as much as 50 or even 100 ohms ; which would be
practically a disconnection from earth.

There would seem to be some danger of the two resistances being
burnt out, in the event of a bad earth on either "outer" occur-
ring while the test was being made, the connections being as in

Fig. 5.

Apart, however, from all questions of safety — for of course the
resistances could be constructed to jointly carry 25 amperes under 250

Fig. 6.

Glasgow AnnAwo^MsnT.
Fig. 7.

volts — the reason why this test appeared to the author to be somewhat
unsatisfactory was that it only measured the combined insulation
resistance of the three mains, and not their individual resistances.

(d) The same objection applied to the test {d) ; with the additional
disadvantage that it involved the entire interruption of the B.O.T.
connection with earth at the time of making the test.

Now, given that the insulation of the systepi has gradually fallen
below the standard — but with no pronounced leak on either pole — the
mere measurement of the joint insulation resistance of the three mains
as obtained from test (c) does not help us as to which pole we are
to look (positive, negative or neutral) for the low state of insulation.

And for the reasons given under Section I. the B.O.T. Ammeter is
just as likely to mislead us, as to help us, in looking for the faulty pole ;
its operation being under similar conditions to those of Raphael's
test (c).

Suppose, for example, that we had 60 feeders, in all, issuing from
the station, viz., 20 positives, 20 neutrals, and 20 negatives, it will

880

TAYLOR: NETWORK TESTS,

tBirminghatrt,

clearly save us a possible 40 unnecessary tests if, to begin with, we
know whether the fault is on the positive, negative, or neutral main.

A test panel, to be useful, should therefore fulfil the following
functions : —

(i) It must indicate on which pole the leak is developing.

(2) It must enable us to ascertain on which of the feeders (con-

nected to that pole) the fault exists. ,

(3) It should enable us "to clear" — or, failing this, to localise —

the fault by a momentary application thereto of increased
pressure ; and yet to limit in amount the current which might
otherwise be put through the fault.

(4) It should not interfere with the existing B.O.T. connection to

earth.

jfl5<«

T T

k "^

.mTfI

"—^

» laaKfk. U^

•H^i

.MMHiTeM.

MANCMRftTCR AlUUHCtWlNT

Fig. 8.

Fig. 9.

The coil P holds the auxiliary 100
amps, pen dff paper. A rush of cuiTcnt
through the magnets E M and P liberates
switch S and auxiliary pen simultane-
ously. The lOA shunt is shorted by the
loOA shunt when switch flies over.

The panel designed by the author, and described earlier in this
paper, is intended as an attempt to fulfil the above conditions.

The method of operating the panel is explained under Section I. of
the paper.

A further reason for a test which will give us the P and N leaks
separately— i.er., the slope of the line AB— is that the B.O.T. Regula-
tions require that, in public supply, the leakage current shall be less
than one thousandth part of the supply current.

Now, the supply current is measured by the sum of the positive and
negative 'bus-bar outputs ; hence the leakage current must be measured
in the same way ; viz., by the sum of P and N. The insulation of the

1903.] AND STATION EARTHING. 881

neutral may be quite low ; but the actual leak M through it is, under
normal conditions, quite negligible.

Hence, if we obtain the joint insulation resistance of all three
mains by any of the tests mentioned, and divide this into 230 volts
(to get the actual leak), we shall be misled into thinking that the
insulation is below the B.O.T. standard when it is really above it ;
nor have we any means of gauging by how far the state oi our mains
really comes short of, or exceeds, the B.O.T. requirements.

Most station engineers would like to be assured on this point, and
all want some standard to work to.

SECTION III.

Relative Efficiency of Different Methods of Earthing.

In considering this subject the two principal things to keep before
us are continuity of supply and safety to the consumer. The con-
tingencies that we have to face, as likely to happen outside the station,
are : —

(i) Earths on the neutral on consumer's premises.

(2) Earths on either " outer " on ditto.

(3) „ „ „ on the system of mains.

(4) Various combinations of these.

In each case the effect of permanently earthing through a moderate
resistance — say 2^3 ohms — will be compared with the effect of a direct
earth connection, whether made through a fuse of large capacity or
otherwise. See Figs. 5, 6, 7, 8, 9.

In Fig. 10 is shown the case of a consumer A whose neutral makes

Fig. id.

an earth connection E somewhere. Here we see that the partial
earth at the station reduces the risk of a portion of the return current
from installations B, C, D, etc., being shunted out of the neutral dis-
tributor through A's premises and the fault on his installation, and so
blowing the fuse / and leaving A cut off from supply — except through
the fault — just as the evening load comes on.

In Fig. II A's installation is sound, but B has a fault E on his

882

TAYLOR: NETWORK TESTS,

[Birmingham,

positive side. In this case the partial earth at the station somewhat
reduces the chance of B having his fuse / blown, and being unable
to get a light when he switches on in the evening.

A further advantage of the partial earth is that in case B's installa-
tion should be a large one, and its fuse graded too heavy, the distributor

Fig. II.

fuse F might be saved from being also blown and all consumers on
that section being put in the same case as B.

It will also be evident that, by means of the author's test panel, the
station engineer can, at any moment, cut out the resistance R at the
station and close his switch S ; thus blowing B's fuse and locating
the fault to a particular feeder.

Also it will be seen that, by means of the fuse on the test panel, the
current could be graded and, if found to be so large as to mean the
extinction of a number of lights, the blowing of the consumer's fuse /
could be deferred, at the discretion of the engineer, till daylight.

In Fig. 12 all consumer's installations are sound, but there is a fault

-'/

Fig. 12.

E on the service connections or on one of the "outers" of the
distributing system.

In this case it is clearly an advantage to have only a partial earth
at the station ; for if the station " neutral " were earthed direct, or
through a heavy fuse, there is considerable risk of blowing the dis-
tributor fuse F and putting the whole of the consumers on that section
in darkness ; this, too, for a fault, not on the consumers' premises, but
on the mains.

Stating briefly the arguments for, and against, earthing through a
resistance in these several cases, we have : —

1903.] AND STATION EARTHING. 883

Fig. io :—

(i) Reduced risk of A being cut off from station just as darkness

comes on.
Fig. II :—

(i) Reduced risk of all consumers on the section being cut off from

supply through^ault on B's installation.

(2) Reduced risk of B's installation being cut off from supply

unnecessarily.

(3) Equal facility for locating from station.
Fig. 12 : —

(i) Reduced risk of plunging all consumers on the section into

darkness, through fault on mains alone.
(2) Equal facility for locating from station.
Figs. 10 and 12 (combination of) ;—

(i) Reduced risk of plunging all consumers on the section into

darkness.

(2) Increased risk of A's lamps being burnt out, through his fuse

/ blowing.

(3) Equal facility for locating from the station.
Fig. 10 and 11 (combination of) : —

(i) Reduced risk of all consumers on the section being cut off from
the supply.

(2) Reduced risk of cutting off B from the supply.

(3) Increased risk of A's lamps being burnt out (through fault on

his own premises).

(4) Equal facility for localising both A and B from the station.
Figs, ii and 12 (combination of) : —

(i) Reduced risk of all consumers on the section being put in
darkness or cut off from the supply.

(2) Reduced risk of faulty consumer being put in darkness.

(3) Equal facility for localising from station.
Figs. 10, 11, 12 (combination of) : —

(i) Reduced risk of all consumers on the section being put in
darkness or cut off from supply.

(2) Reduced risk of cutting off B from supply.

(3) Increased risk of burning up A's lamps.

(4) Equal means of locaUsing A and B and faulty distributor.

Summary of " Pros " and " Cons,'*

Figs. 10, 11, 12. — These are the most likely cases, requiring the
fewest combinations of accidents ; and in every one of these the con-
ditions are favourable to inserting a resistance permanently at the
station between the neutral and earth.

Figs. 10/12, lo/ii, 10/11/12.— These are, in the main, favourable to
the change. The faulty consumer is the only sufferer, which is but
right.

Fig. 11/12. — This case, again, is all in favour of the change.

There seems, therefore, a distinct preponderance of argument in
favour of inserting the resistance.

884 TAYLOR: NETWORK TESTS, [Birmingham,

The above conclusions do not consider the possibility of the fuse,
which makes the "dead earth" connection, melting.

It may be argued in favour of having a fuse that, by employing a
light fuse to shunt the earthing resistance at the station, the consumer's
fuse is saved from blowing (see Figs. lo and ii), in the case of a light
fault. ,

The answer to this is that, in Fig. lo, the current would not have
attained to the dimensions indicated by the blowing of the station
fuse had this fuse not facilitated its flow by being placed to shunt the
resistance ; while, in Fig. ii, the fuse might as well have been absent,
for it cannot be replaced till the consumer's fuse has blown ; and, if
the latter do not blow with the former, then neither would ii have
blown had there been no fuse, but only the resistance. In the case of
a " dead earth " fault the consumer's fuse is sure to go, anyway.

If, on the other hand, we employ a heaiy fuse at the station to
shunt the resistance we shall have, in the case of a bad fault on
consumer's premises (Fig. ii), both current and pressure available at
the fault, or at the consumer's fuse, sufficient to maintain an arc, or
do other damage, many times greater than if there had been no station
fuse at all.

Further, the fuse involves us in automatic devices, and in two
scales, for the B.O.T. Recording Ammeter.

All seems to point, therefore, in favour of having a resistance
without a fuse to shunt it.

Current-Carrying Capacity of Earthing Resistance.

It will be noted that the current which the resistance is designed
to pass (under 230 volts) should bear a definite relation to the current
at which the smaller sizes of distributor fuse are set to blow.

If primary importance is to be given to the prevention of the blow-
ing of distributor fuses (due to " earths " in distributors, or on premises
of large consumers), then the resistance must not allow a current to
pass sufficient to blow the smallest distributor fuse— or, if the section
be fused from both ends, the pair of fuses.

On the other hand, if the earth potential is to be kept, at all costs,
as near to the neutral potential as possible, the resistance must be as
low and have as large a current-carrying capacity as possible ; but in
this case we shall have distributor fuses — perhaps even feeder fuses —
blowing on the smallest provocation.

Taking into consideration the fact that, with the panel devised by
the author, the engineer can blow any distributor fuse (on a faulty
distributor) at discretion, the safest course would appear to be to design
the earthing resistance so as to save the distributor fuse or fuses, and to
connect an alarm bell between the neutral 'bus-bar and earth, to ring
with, say, 50 volts. The engineer can then close the switch S, Fig. 10,
when the bell rings, first through a fuse insufficient to blow the
distributor fuses ; and then, if this still fails to clear the fault, through
a heavier one ; or if the voltage is not much over 50, he may elect to
risk leaving it alone.

1903.]

AND STATION EARTHING.

885

Earthing the Neutral at Feeding Points only.

•

The argument for earthing at this part of the system is, the author
believes, principally that currents from faults on consumers' premises
would form local circuits from the faults to the nearest earth connec-
tion, instead of, as now, having to traverse the whole town in order to
get to the generating station. There would thus, it is argued, be less
probability of interference with telephone circuits, gas and water
pipes, etc.

The argument appears to be intended to apply only where there is
a completely earthed neutral over the whole distributing system (the

F F" F^

Fig. 13.

author shows later that it does not altogether hold here either). For if
there be any resistance inserted — the diagram (Fig. 13) shows that a
comparatively small " outer " leak will divert the potential of the earth
by, say, 100 volts from that of the neutral.

The result of this will be that not only will the local earth plate of
the particular section of distributing system be thus called into opera-
tion, but the whole of the other earth connections as well, thus
settrog up a network of earth currents all over the city.

Fig. 14 shows this condition of things, and the connections at the
station for the author's test. It also suggests the undesirability, where
there are substations in a town, of interlinking the networks supplied
by these substations with that supplied by the main station, or with
one another.

886

TAYLOR: NETWORK TESTS,

[Birmingham,

Risks with the Neutral Completely Earthed,

If, to avoid the difficulty described above, we cut down the resist-
ance materially at the earthing points, we come to what is practically
a direct earthing of the neutral at each distributing centre. It is true
that we have now practically eliminated the chance of a consumer's
fuse blowing under the conditions of Fig. lo ; but have we not jumped
out of the frying-pan into the fire ? For it is impossible to conceive
that the whole of the feeding centres of the town will always, as re-
gards their neutrals, be at the same potential above or below the earth
except by the flow of large earth currents from one centre to another.

Fig. 14*

We shall have invited this by reducing the resistance so low between
neutral and earth at the various centres ; for the neutral feeders all
come off a common connection at the generating station, and the
" drops " in the feeders cannot conceivably be all equal.

The argument still holds to some extent, even though the neutrals
be earthed continuously throughout the distributing system.

Again, all the disadvantages enumerated earlier against the reduc-
tion of the earthing resistance at the station still hold in their most
aggravated form.

Testing with Neutral Completely Earthed,

It looks as if any attempt to measure the insulation resistance of the
outers under such conditions would be unsuccessful, without discon-
necting sections one by one.

The importance of being able to measure the insulation of, and to

1908.] AND STATION EARTHING. 68?

localise faults on, each pole in turn, by a momentary earthing of one of
the others, can hardly be over-rated.

Hence the use of a bare neutral distributor will, on this score alone,
be distasteful to the average station engineer.

Again, since the state of the insulation of the '• outers " is unknown,
there may be considerable leaks developing all over the system, with
the insulation gradually falling ; but nothing will be known of it (the
B.O.T. Ammeter has been "scrapped") till it becomes sufficiently
accentuated in one spot to cause a fuse to blow.

Thus the insulation will get lower and lower, with no means of
checking, or putting suspected parts under sufficient pressure to break
down the fault.

A system which keeps the " outers " up to a definite standard seems
to the author the only possible safe one, and this is not to be obtained
where the neutral is completely earthed ; nor where the earth connec-
tion, if direct to earth, cannot readily be removed by the station
engineer for purposes of testing.

Conclusion,

It seems, on the whole, as though the most satisfactory all-round
method were to earth permanently through a resistance and at the
station.

When the connection is made through a fuse, without other resist-
ance permanently in circuit, as is now rather general, it would seem
that, the moment the fuse goes, all control of the rise of potential of the
earth is taken out of the engineer's hand ; and another fuse cannot
easily be inserted unless the B.O.T. connection be entirely opened,
when the voltage of the earth might be practically that of either of the
" outers."

In conclusion the author hopes that this effort to draw discussion on
a subject which seems to him to have been insufficiently ventilated,
may not be considered a meddlesome interference with things which
have long been settled.

APPENDIX.
Note I. — Change of Potential of Earth due to Fault on

EITHER "outer" MAIN.

Fig. 13 has been prepared to show the relation between : — (i) the
current flowing through a fault on either " outer " ; (2) the current in
the B.O.T. Recorder ; and (3) the rise of potential of the earth itself
as compared with neutral B/B potential.

The fault corresponds with a momentary demand of about 34
amperes on the positive side of the station (or 39 amps, if we include
the normal positive leak), the actual current through the fault being
given by the ordinate enclosed between the new " datum hne " and
the old, at the proper potential (viz., 74 volts).
Vol. 82. 58

ddS TAYLOR: NETWORK TESTS, [ Birmingham,

The lines E' F, E" F", E'" -F'", correspond respectively with 2*3
1*15, and 20 ohms in the B.O.T. connection ; and the potentials of
earth are given by their intersections with the base line.

The normal position of the P — N line is shown by AB and the
temporary position, due to the fault, by A'B.

The potential of earth, due to the fault, changes by 64* volts when
2*3 ohms are in the B.O.T. connection and by 30* volts when i*i5 ohms
are employed.

If 20 ohms be employed in the earth connection — a not unusual
value — the rise of potential, due to the fault, is no less than 145-150
volts.

The currents traversing the B.O.T. ammeter are also clearly shown.

In Fig, II B's fuse / would carry, or blow with, the 34 amperes,
there being 2*3 ohms in the station earth connection.

Mr. Raphael. Mr. F. CHARLES RAPHAEL (commufticatcd) ; Mr. Taylor has been
kind enough to mention in his paper a method of testing the insulation
resistance of networks during working which I suggested six or seven
years ago. At that time I was preparing the book to which he alludes
in his paper, and I made inquiries to ascertain what periodic tests were
being made of the insulation resistance of networks. I was then rather
in the position of a specialist, being usually only called in to locate the
trouble and operate when the case had reached a critical point, and I
was anxious to learn from the family practitioners how they diagnosed
the disease of mains breakdown in its incipient stages. To my surprise
I ascertained that the testing of networks for insulation was compara-
tively rare. The two or three engineers who did test them employed
Frisch's method of connecting a voltmeter or ammeter between each
main and earth when, as is well known, the insulation resistance of the
whole network is calculable from any two of the readings.

Just then the 2 x 220 volt three- wire network with the neutral
conductor earthed at the station was coming into vogue, and I there-
fore suggested the middle-wire ammeter method of measuring the
insulation of the network mentioned by Mr. Taylor. Perhaps I may
be allowed to explain here what this test is, as I am bound to confess
that I did not recognise Mr. Taylor's Fig. 5 until I read in the foot-line
that it was " Raphael's test," and it therefore may not have been clear
to others either. An ammeter (either having a long range or appro-
priate shunts) is connected between the middle wire and earth through
a resistance which is normally short-circuited. To make the test, the
short circuit is removed, and a reading d^ is taken. Then the anmieter
and resistance is shunted with a resistance equal to the series resistance
plus the resistance of the ammeter, and a second reading d^ is taken.
If r is the resistance of the ammeter plus its series resistance, the

insulation resistance of the network is * - ' r. This method would

2 i/a — a,

appear to be applicable without the second ammeter, which Mr. Taylor

designates " Board of Trade " ammeter in his Fig. 5. The resistance r

would have to be of the same order as the insulation resistance of the

network, and thus it must be normally short-circuited, as the function

1908.] AND STATION EARTHING: DISCUSSION. 880

of the earth on the middle wire is not fulfilled unless the resistance of Mr. Raphael
this earth connection is a fraction of the fault resistance of the other
mains.

I do not know whether this suggestion has been acted on to any
great extent. I believe not, and that, when tests are taken — which is
rare, — the earth on the middle wire is removed for a few moments, and
Frisch's test is made. It may be noted that it is only necessary, in
making Frisch's test, to earth two (any two) of the three wires through
an ammeter or voltmeter, for the insulation resistance — as well as the
reading which would have been obtained from the third wire — is
calculable from the two readings.

It appears to me that, whatever method is employed for measuring
the combined insulation resistance, this insulation resistance compared
with the middle-wire ammeter reading will indicate on what main a
fatilt has developed. Normally, for instance, the current through the
middle- wire ammeter is from the middle wire to earth, indicating that
the insulation of the negative main is worse than that of the positive
main. Suppose this to be the case, and that the test of the combined
insulation resistance one day gives a lower result than usual : if this
is accompanied by an increase in the middle- wire ammeter reading,
it indicates a decrease in the insulation of the negative. If, on the
other hand, the middle-wire ammeter reading is below the normal,
in spite of the decrease in insulation, the fault will be on the positive
or neutral, the effect of a fault in the neutral wire upon the ammeter
deflection being relatively less than a fault in the positive.

Coming to Mr. Taylor's suggestion, I must own that, with the limited
time at my disposal, I have been unable to understand entirely the
method he proposes. Has he checked his graphical explanation by an
analytical proof, or by employing Mr. Alexander Russell's ingenious
load diagrams ? Perhaps in his reply to the discussion he will be good
enough to make his method a little clearer. If he is really measuring
the current leaking away from each main separately, his test should be
most useful ; but, if his method is a rough approximation only, and is
influenced by the load on the network, a simple method such as Frisch's
or *' Raphael's " is preferable in my opinion. A momentary disconnec-
tion of the earth on the middle wire for the former method is not likely
to be attended with serious consequences, and a momentary increase
in the resistance in the middle-wire earth for the purposes of the latter
method would surely be quite harmless.

Mr. Taylor has done good service in calling attention to the necessity
of testing electric light networks, and I trust that his paper will not
lead to the opinion that such tests are comphcated or difficult to carry
out. The contrary is the case; testing the insulation resistance of a
network during working is one of the simplest electrical measurements.

Mr. Alexander Russell (communicated) : I regret that I shall be y^^ rumcil
unable to be present at the meeting, especially as tliere arc one or two
points in the paper which I fail to grasp. The diagrams would be so
much more easily understood from Mr. Taylor's explanations. The
absence of formulae also makes it difficult to follow the methods, and
makes it almost impossible to gauge their accuracy. I have attempted

890 TAYLOR: NETWORK TESTS, [Birmingham,

Mr. RusmU. to supply some of these formulae with, however, only partial success.
My attempts will enable Mr. Taylor to see whether I have understood
him or not, and may probably be of assistance to others. The author's
solution is deserving of the most careful study by station engineers.

In ray paper published in the journal and referred to by Mr. Taylor
it is shown that if we make an artificial leak to earth from any of the
mains, and if V — V be the simultaneous change in the P.D. between
each of the mains and earth, then

c ^'

where C is the current in the leak, and F is what is called the insulation
resistance of the network. For various reasons the value of F is always
altering slightly, so that a very accurate measurement of it is not wanted.
Now, since the earth connection of the middle is an artificial leak,
therefore

— c ^-

Where V, is the P.D. between the middle and earth when the earth
connection is removed, V, is the P.D. between the same points with
the earth connection in its place, and C is the current in the earth
connection. If we plot a curve with V, for abscissa and C for
ordinate, then we get the line C D in Fig. i. If we alter the resistance
of the earth connection, then

- -^ P,

and hence

p _ v. - V '.

The drawback to this method of measuring F is that V, — V", is only
about lo volts, and it is not a steady voltage. Also, since F is about
lo ohms, C — C is about an ampere, and could not be determined
with any great accuracy. I should certainly not use this method.

Another method — and this, I think, is the method Mr. Taylor uses —
is to make an artificial leak on either of the outers. In this case we
have

V. — V. _ FR_^
C ^ F + R'

where C is the current in the leak and R is the resistance of the

earth connection. This is the equation to the line EF in Diagram i.

. Since we can make V, — V, equal to 200 volts or so, we can determine

p „ easily to within two or three per cent. Hence, unless F is

large compared with R, we can determine it approximately when we
know R.

It seems to me that it is unnecessary to worry ourselves about how
to measure the insulation resistance with the earth connection in its
position, seeing that it is perfectly simple to open this connection during

1903.] AND STATION EARTHING: DISCUSSION. 891

the few seconds required to measure F. In the network considered Mt.Rmmil
the potential of the negative outer would then be — 280 volts, and this
is not very alarming. The author seems to have had the neutral at
200 volts, and therefore the P.D. between the negative outer and earth
must have been — 430 volts during his test.

I hope Mr. Taylor will explain a little more fully the principle of
the method he uses for measuring the leakage current in the middle
main, as if it can be done accurately, or even if it can only be done
roughly, it represents a very considerable advance in pur knowledge.
It is easy to devise theoretical methods of doing this by keeping the
two sides of the three-wire system at different potentials during the
test, but the only methods known to the writer are too elaborate for
practice.

The author seems to put a resistance in series with the neutral
leaks, but as this resistance would be traversed also by the consumers'
out-of -balance load, and as its resistance is very small compared to the
resultant leak on the middle main, I fail to see how he manages to
separate out the middle leak.

In most three- wire networks, when we alter the potentials of the
mains, the fault resistances of the three mains vary, although the
insulation resistance F of the mains remains the same. Hence we are
not justified in assuming that the resultant leakage current from a main
and the wires connected with it varies as its voltage from earth.

Since the distributing mains are underground and cannot be
inspected, it is of vital imfJortance to the working of the station that
they should be subjected to periodical electrical tests. Mr. Taylor's
testing panel is therefore a step in the right direction, and is deserving
of the highest praise. Even if he has not succeeded in separating out
the three leaks, we can determine the insulation resistance of a network
rapidly by its means, and an inspection of these records will be of far
greater value than an inspection of the record of the leakage current in
the earth connection.

Mr. A. P. Trotter said they were greatly indebted to Mr. Taylor M*"- Trotter,
for the paper, and also to those members who had asked him to give
further explanation ; for he had read the paper through twice, and he
had been greatly puzzled by Fig. i ; but a great deal of it was made
more clear by the explanation of the diagrams placed before them
that evening, and the way in which Mr. Taylor described how the
p)otential of the earth was pulled over in one direction or another by
the ammeter was very interesting. He only wished he could follow
how the ordinary out-of -balance current affected this ; he did not quite
see how that would be. He should understand it in a perfectly well-
balanced circuit — however, he would not go into details on that matter.
He was puzzled very much over what was the meaning of the height
of the ordinate (A,) in Fig. i. Under the normal circumstances, when
there was no leak at all, Mr. Taylor began with the ordinate and a slope
to the datum line. There was a normal diagram with no leaks at all,
and then there began to be slopes representing the leaks. He was glad
Mr. Taylor had called attention to Mr. Russell's paper in Vol. 30 of the
Institution journal; it was an extremely interesting one, and most

892 TAYLOR: NETWORK TESTS, [Birmingham,

Mr. Trotter, unfortunately was not in the index of that volume. It was a paper
attached to No. 148 of that volume. Mr. Russell dealt with the problem
like a steelyard. He took the centre of gravity as the neutral point at
which, if you made a connection, there would be no leak ; and he
took the faults as loads on the bar, and treated them from the point
of view of moment. He (Mr. Trotter) thought Mr. Taylor's method of
diagrams, when fully explained, might be a still better way. Some
people were more fond of algebra ; but he was one of those who
preferred a diagram when he could understand it. Mr. Taylor
described the various ways in which the stations were earthed. He
(Mr. Trotter) had to go into a good many stations, and he very often
asked the engineers how they earthed their middle wire, because he
wanted to know ; though it was not part of his duty because, fortunately,
there were no Board of Trade regulations describing how it should be
done. The general principle, he believed, of connecting the middle
wire was to prevent any consumer getting more than a 250-volt shock.
He believed that was the object, because the regulations began by
sa)dng he must be liable to no more. Of course, if there was a three-
wire network, and there was a leak on the negative, up went the
positive, and a man might get a shock off it. There was no harm in
opening the earth connection at the proper time for a few seconds, but
there was the stress you put on the wiring ; a bigger stress was put
upon the wiring than it was usually intended for. The use of the
ammeter was not by any means universal. He came across works the
other day in charge of a young engineer where there was no ammeter,
no fuse, no switch — but the earth dead connected up. He hoped it
might be so for long, but he fancied the engineer had something to
learn, and he would no doubt have recourse to one of these devices.
Some time ago he (Mr. Trotter) had to do with a very serious gas
explosion. The gas company declared that the electric mains had
exploded, and laid it all down to them, and he had to investigate it.
He went to the works and asked how their middle wire was connected.
It was connected to a recording ammeter ; they showed the record for
the day with the line dead straight and at zero. He asked the gas
company if they had any instrument that would show their leaks, and
they had not got one. One of the first recording ammeters he saw
was at Glasgow. Mr. Chamen had found it most useful in tracing
the leaks. He imagined that the use of that device would become
very much more common than it was now. He once discussed
what there should be in addition, at a meeting of the Municipal
Engineers, that being, he believed, the first occasion on which
the subject had ever been dealt with, though it was a most im-
portant subject. It seemed that there should be a resistance, otherwise
there would be a dead short ; such a resistance should be provided
that at all events the plant could handle the current ; some engineers
suggested 10 or 20 ohms resistance. This was too much, and would
defeat the object of earthing. He thought that the normal condition
should be a dead earth on the middle wire, and a circuit-breaker set to
open with a heavy current, throwing in a resistance and giving an alarm
signal, and perhaps alterinjg the sensitiveness of the recording ammetefr

1903.]

AND STATION EARTHING: DISCUSSION.

Then came the question, if there were a heavy leak on the negative, Mr. Trotter.
how much would the positive go up ? As Mr. Taylor had said, putting
that resistance in would hold the middle wire down, and Mr. Russell
went so far as to say that he would like to put the resistance in the
sounder main to hold it down. He treated it from the point of view
of a balance ; if a heavy leak came on and pulled it down, he would
like to put an artificial leak on the other end to hold that down ;
but a smaller leak at a greater leverage. He said it would con-
sume so many kilowatts, and those might be useful in the station.
But he (Mr. Trotter) thought no engineer had ever driven his pump,
off that source of energy. He asked the people who had suggested
ID or 20 ohms in the earth circuit what they would do if there were
a bad fault. Would not the sounder main go up above 250 volts ?

Mr. Russell's paper enabled one to calculate with some trouble, and
he hoped that Mr. Taylor's paper would, when carefully considered,
enable one to calculate with more ease. What was the maximum
resistance that could be put to earth so that the sounder mains should
not rise more than 250 volts above earth when a heavy leak occurred
upK>n the other one ? One railway company objected to some people
putting their middle wire to earth at all ; they said they would disturb
their signals very much, but they added that if the people in question
would put 1,000 ohms between there and earth, they would not raise
any further objection. He wished to raise a little protest about any
fuses or switches at all in middle wires. These troubles, it seemed to
him, would be got over by considering the middle wire was at earth
potential. The only way in which it could differ from earth potential
was by a few volts owing the drop due to the current itself. If a leak
occurred in a consumer's house, as was shown in one of the diagrams,
what harm could happen as long as there was no switch and no fuse
between that leak and the middle wire ?

Mr. Taylor : Are you alluding only to fuses on consumers* premises Mr. Taylor,
or in the distributing main as well ?

Mr. Trotter : Anywhere. Mr. Trotter.

Mr. Taylor : Because no fuses are shown on the neutral distributing Mr. Taylor.
main.

Mr. Trotter said it was rather startling to some people, but he Mr. Trotter.
believed Major Cardew held from the first, and he knew a good many
engineers also held, that there should be no fuses and switches at all
on any wire connected with the middle wire ; let it all be considered
to be an earth potential. Although he regarded that as earth potential,
he was one of those who held very strongly that the middle wire
should be earthed at one point only and insulated at all other points,
as the Board of Trade asked. There had been a good deal of talk
lately over the German system of abandoning insulation altogether on
the middle wire, and having it earthed all over the place, but Mr. Taylor
showed one or two reasons why that would be undesirable. Under
such a system it would be impossible to make any tests at all : there
would not even be the recording ammeter at the station to tell what
was going on. He had hardly found any engineers who wanted that
system e^ccept they wanted to pick up village lighting on the cheap.

894

TAYLOR: NETWORK TESTS,

[Birmingham,

Mr.
Duesbixry.

Mr. Trotter. It was fair to say that they claimed that leaks would develop rapidly
into shorts, and that this result would tend tp the happiness of the
greatest number ; but he was not convinced. But they were in the
habit, he believed, of putting in insulation in excess of the work
it had got to do. Why insulate for 250 volts? It was never going
to get that; let them insulate it reasonably. As Mr. Taylor had
said, if they set up a network of earth currents all over the city,
and could not get at them to test them, it would be liable to give
rise to very serious difficulties. It was quite a common practice to
open the earth connection for making a test, but if Mr. Taylor's paper
would enable engineers to make their tests without opening the earth
connection, he thought a very great step in advance would have been
made.

Mr. T. DuESBURY said that he could thoroughly endorse Mr.
Taylor's reasons for a new test. He regarded the disconnection of
the middle wire from earth for testing purposes as inadvisable, as it
threw a great strain on the wiring. The knowledge that in the test
described by Mr. Raphael the combined insulation only could be ob-
tained, had, despite the regulations of the Board of Trade on the point,
led most engineers to trust more or less in Providence, which trust was
apt to be occasionally badly shaken. He could strongly endorse Mr.
Taylor's views as to the middle wire permanently earthed through a
low resistance being absolutely the best method of earthing, as he had
experience of two other methods — earthed direct without any fuse, and
earthed through a low resistance short-circuited by a fuse. It was
unnecessary to consider the first, as the foolishness was apparent. The
second method had one very weak point, that the advantages of low
resistance were only utilised in the case of a fault sufficiently bad to
blow the fuse, and consequently cut in the resistance. For some time,
he ran at Sutton Coldfield with the middle wire directly earthed, but
during the last nine months he had inserted between the middle wire
and earth connection a resistance of 4 ohms, able to carry 60 amperes
continuously, and he could confidently say that the number of cases
of consumers' main fuses blowing had decreased by at least 50 per
cent. He could also speak of the value of the recording ammeter in
the way of locating small faults. On account of the big earth currents
which must flow between feeding-points, he regarded the earthing of
the network at feeding-points as altogether wrong, and he thought, if
anything, he should much prefer the middle wire earthed throughout
its whole length. Although quite foreign to the subject under discus-
sion, he should like to remark that in some cases too little attention
was frequently paid to the method of making the earth connection
itself, and consequently the earth plate had an appreciable potential
difference to the earth surrounding it. He recently heard of a case
where the engineer connected the middle wire to the exhaust-pipe
system, and seemed quite pained when he had to buy new boiler blow-
down cocks within twelve months.
Mr. Groves. Mr. W. E. Groves (communicated) : While fully appreciating the
importance of Mr. Taylor's paper, and particularly of the analytical dia-
gram. Fig. I, I cannot regard the test as it stands as likely to be of any

1908.] AND STATION EARTHING: DISCUSSION. 896

great service for frequent station use — say, twice daily in the morning, Mr. Groves.
and at top load.

It should be possible for a " switchboard attendant " or his equiva-
lent to report the state of the insulation when required to do so, particu-
larly when there are several stations or substations, and I am z^raid if
Mr. Taylor's test were used in this way it would too often produce
unsatisfactory results. Of course the idea of discriminating between
the fault resistances of the three poles is most attractive, but facts are
of greater importance than figures.

Mr. Alexander Russell's paper referred to by Mr. Taylor is a most
valuable one, and the simple insulation test described in it very strongly
commends itself to me. It involves the opening of the earthing switch
momentarily, and this switch could be controlled by a spring to prevent
its being left opened accidentally.

Normally, the D.P. between neutral and earth, if the switch were
opened would be less than that involved by Test No. 3. The last-named
test also involves the flashing about of considerable currents and volt-
ages to the detriment of instruments and switches ; it should be therefore
only resorted to when the insulation has fallen too low. Referring to

V V V

Mr. Russell's simple formula F = ' — -, — - is the resistance of

the coil in series with the B.O.T. instrument ; the test therefore resolves
itself into a'reading of ammeter in the earth connection and a momentary
breaking of earthing switch to read V,.

It is an easy mental operation to divide the latter by the former and
diminish it by R. If F is high and R low (say 2 or 3 ohms), the latter

may be neglected so that F is simply — ^. If F is above the selected

standard the test is completed. If the test shows that F has fallen too
low, the faulty or the most faulty pole will usually be indicated by volt-
meter. If there are faults on both sides the removal of the greater
reveals the less.

Occasionally we may be confronted with the voltmeter refusing to
move appreciably when the earthing switch is broken, which would
mean that the P and N leaks were exactly balanced (a condition of things
rarely existing in practice) or that M is faulty. In this case having
the voltmeter in front of us reading near zero there is no harm in leav-
ing the earthing switch open, as it can be closed immediately the volts
rise. This would avoid heavy current through the B.O.T. instrument
while you perform what is a rough Test No. 3. If the neutral is sound
the flashing will not effect the neutral ammeter, if otherwise, a " kick "
will result. If outers are at fault the ammeter on the pole opposite to
that flashed to earth will ** kick." With suitable arrangements the

V
switchboard attendant can easily read — , and if he reports that the

insulation is down, the analysis of F can be undertaken by the mains
superintendent.

Obviously the essential difference between Mr. Taylor's and
Mr. Russell's tests is that the former reads A, (vide Fig. i)and the
latter volts between neutral and earth when earthing switch is open.

896 TAYLOR: NETWORK TESTS, [Birmingham,

Mr. Groves. Mr. Taylor does not read the cotangent the angle C D makes with
the horizontal directly, and A A, and A, must be very accurately read,
but neither does he open the earthing switch. Mr. Russell reads
this cotangent more directly as the expense of opening the earthing
switch. I do not think any apology for opening the earthing switch is
necessary if the insulation resistance can be more readily ascertained
by the operation, particularly as the switch need only be opened for a
moment.

The testing panel as designed by Mr. Taylor lends itself admirably
to the performance of Mr. Russell's test as well as that devised by Mr.
Taylor. It also permits the modification of the test suggested above
being very readily carried out.

As a record of change and occasionally indicating to what kind of
apparatus a fault is due, the B.O.T. recording ammeter is valuable, but
the fallacy of relying on it to indicate the state of the insulation does
not require emphasis.

Concerning the method of earthing. There should be no senti-
mental objection to blowing a consumer's fuse if a fault should develop
in his installation.

The earthing resistance should be sufficiently low to allow currents
to pass which will blow, with perhaps a few exceptions, the largest
consumer's fuse should his insulation break down.

Any fuse in the network should be sufficiently heavy to avoid risk of
a faulty consumer putting his neighbours in darkness.

Earthing without control would render efficient supply impossible
and bring the business into disrepute. It would be small satisfaction to
consumers to be told that supply could not be given because of a fault
for which they may be in no sense responsible. Consumers would often
be at the mercy of the industrious navvy who may have inadvertently
driven into the supply mains.
Mr. Aahiin. Mr. F. J. W. AsHLiN {communicated) : The test for obtaining actual

readings of neutral leakage on a three- wire system seems a distinct step
in advance of what could be previously determined by known methods.
Such a test panel should be a welcome adjunct to any central station,
giving a station engineer a ready means of knowing the state of the
insulation of the supply system at any time.

From practical experience of the use of the panel as described I
think that readings taken when a moderate fault d^voXoipsJollowed up by
actual search to locate the leakage^ will in many cases save the ultimate
annoyance of possible heavy short-circuits, sometimes blowing the
feeder fuses at the station end during time of heavy demand.

I would point out that the test panel as described would not appear
to be so necessary when a leak develops on any feeder, amounting to a
*'dead earth." Assuming a differential reading B.O.T. recording-am-
meter is used, this will at once show by the deflection on which side the
leakage is taking place, and the result can generally be seen at once on
the feeder ammeter on the switchboard in the extra load recorded.

If a fault of this magnitude comes on, say, before or during heavy
load on the station, the earthing resistance (as advocated by Mr. Taylor)
must carry its full current the whole tipie until the fault can be located

1903.]

AND STATION EARTHING: DISCUSSION.

897

or cut out At such a time it would be an advantage to be able to Mr. AshUn
insert other resistance in parallel with the station earthing resistance.

If, by any chance, the earthing resistance is subjected to double the
voltage for which it was designed, say, 400 to 500 volts, through, say, a
complication in a street box, the consequences to the resistance itself
ivonld be rather disastrous !

As regards the instruments — ammeters and voltmeters — used on the
test panel, these require to be particularly accurate and should be fre-
quently calibrated, as the effect of " pulling the potential hard over" is
rather severe on the instrument. Any error would apparently be multi-
plied considerably if referred to the lines of Fig. i, and would give
misleading results as to the actual amount of leakage.

Instead of an accumulator cell and ammeter for the neutral test (as
the cell requires attention by a battery attendant), would not an ordinary
small 2-volt cell be sufficient, with a voltmeter to measure the drop of
potential ?

Mr. A. M. Taylor {in reply) : Mr. Alex Russell describes his own test, Mr. Taylor.
which I quite recognise as a most useful and simple one. It is one which
the consideration of Fig. i led me to several months ago, before I had
unearthed Mr. Russell's paper ; but having set myself the problem of
devising a test which should not interfere with the earth connection,
I (perhaps wrongly) rejected it as a solution of the question.

Mr. Russell suggests that my method is to make an artificial leak on
one outer and measure the current in it. That is so, as regards the
first part of my test, which only carries us as far as the obtaining of the
joint insulation resistance of the three mains, indicated by the slope of
the line (C D) in the diagram. Fig. i.

The second part of the test is quite distinct from this, and consists
of what we may call a " discriminating " test. By means of the artificial
leak we can cause the potential of the earth to travel away from that of
the neutral 'bus-bar to any desired extent — say 200 volts. This puts
the neutral leak of the system under 200 volts, and if the insulation
resistance of the neutral system were 10 ohms then 20 amperes would
flow. This would increase or diminish the algebraic sum of the current
in the neutral feeders by that amount.

Suppose that, prior to making the change in the earth potential,
and immediately after making the first part of the test (which left the
earth potential at that of the neutral 'bus-bar), the out-of -balance
current of the station is found to be, say, 50 amperes, then, on closing
the artificial leak so as to put 200 volts on the neutral leak, the
momentary increase in the out-of-balance current will be 20 amperes,
and on opening the artificial leak again it will diminish to its original
value of 50 amperes.

We should thus know that the neutral leak alone had a resistance of
10 ohms ; and, having previously measured the joint insulation
resistance of the three leaks, it is the easiest thing to deduce the
combined insulation resistance of the positive and negative leaks
without the neutral leak.

Mr. Russell's question as to whether the current through the leaks
fealty obeys Ohm's Law or not is a piost interesting one ; because^ if it

898 TAYLOR: NETWORK TESTS, [Birmingham,

Mr. Taylor, did not, it seems that all tests hitherto considered are valueless. I am
glad to be able to assure Mr. Russell that it does. On a particular
town's system, appljring the " discriminating" test, I found the neutral
leak to be : —

15 amperes under 200 volts
7i »t »» 100 „

3 »» » 50 »

indicating — especially as the last figure could not be measured very
exactly — a very good agreement with Ohm's Law.

Mr. F. C. Raphael suggests that by means of his test he can really
discriminate between the leaks. The method he suggests is to measure
the joint insulation resistance (F) of the three leaks, and compare this
with the B.O.T. Ammeter reading.

In any case we only can by this method measure the change in the
resistance of any one main — not its actual value. If things are to be
kept up to a standard — the B.O.T. standard — we must be able to
measure the actual value.

Mr. Raphael questions the correctness of the diagram Fig. i, but I
think the fact that the equations, both for Mr. Russell's test and for his
own, can be deduced from it are a proof of its accuracy. Mr. Russell has
apparently accepted it, for he has pointed out that the joint insulation
resistance (F) as measured by his test gives the slope of the line (C D)
in my diagram.

In reply to Mr. Raphael's inquiry whether the discriminating test is
not affected by the load on the network, I may say that in the reply to
Mr. Ashlin's remarks I- have gone into this question somewhat more
fully than in the pap6r itself.

Mr. A. P. Trotter asks the very pertinent question : " If we have a
heavy leak on the negative, by how much will the positive 'bus-bar
potential rise above that of the earth ? " I- submit that Fig. t fully
indicates the principles on which we can determine this, and in Fig. 24
(shown among the lantern slides, and now incorporated in the paper)
the actual rise of potential of the earth towards that of the positive
'bus-bar, for a given fault on the positive system, and for three difiFerent
resistances in the B.O.T. connection, is shown clearly. Fig. 2 of the
paper will help Mr. Trotter to apply this diagram in a similar way for
the determination of the conditions accompanying the leak on the
negative.

Mr. Trotter also asks what is the meaning of the ordinate (A.) in the
diagram, Fig. i. It is the value of the current which must be put into
the artificial leak (see reply to Mr. Russell) in order to bring the
potential of the earth to that of the neutral 'bus-bar. In other words,
it is the amount by which the normal positive leak is greater than the
normal negative leak when both are under the same pressure of
230 volts, and is therefore =s (P — N). I am encouraged by Mr.
Trotter's remarks to hope that the diagram given in Fig. i will prove
useful to those engineers who like something which enables them to
picture graphically what goes on, instead |0f having to arrive at it
deductively from formulae.

1903.] AND STATION EARTHING: DISCUSSION. 899

Mr. Dcwsbury's experience is very interesting, as quite confirming Mr. Taylor,
the conclusions in the paper as to the advantage of earthing through
a resistance alone, and with no fuse whatever in connection with that
resistance.

Mr. Groves makes the remark that Mr. Russell's test is more con-
venient than mine, and is less complicated in the formula used.

The formula for my test is —

the resistance in the earth connection being made equal to 2 ohms.
There is no great complication about this, and I think his complaint is
caused by his setting off the two tests I suggest — the combined insula-
tion resistance test and the " discriminating " test — against the one test
of Mr. Russell.' But to get the same information as Mr. Russell's
test gives, it is only necessary to perform the first part of the test (see
remarks under reply to Mr. Russell), and this consists of the simple
observation of (V,), the normal voltmeter reading, and of (A,) the
current in the artificial leak when we close the circuit of the same and
adjust the sliding resistance switch shown on Fig. 7 of my paper.

On the question as to whether a discriminating test is always
necessary, as a day-by-day operation, I am inclined to agree with Mr*
Groves that it is not. It is merely useful in enabling us to know
whether the insulation of the two outer mains comes up to a standard —
say the B.O.T. standard of a combined leak not exceeding one-
thousandth of the station output — and so preventing the mains
superintendent from hunting for faults on the outers which the low
insulation of the neutral has led him to imagine exist there.

Mr. Ashlin suggests a more easy way of measuring the neutral leak
than that employed in my "discriminating" test. Such an arrange-
ment as he suggests it was my intention to describe on the occasion of
reading the paper ; but it was necessary to postpone its description to
another occasion on account of the lateness of the hour.

It is easy to arrange such a circuit as Mr. Ashlin suggests, i.e., with
a single Leclanche cell and a voltmeter, graduated in amperes ; but the
difficulty is the continually-varying magnitude of the out-of-balance
current of the station.

The way in which this may be overcome is as follows : Off the plate
resistance shown in Fig. 7 let there be taken 1 1 wires or tappings, thus
dividing the resistance into 10 equal parts.

Connect the free end of No. 11 wire with a source of E.M.F. of
o*2 volt (a couple of small cells of different types set to oppose one
another will do), then continue it through a central-zero voltmeter,
sufficiently sensitive to read loo* divisions of scale with 02 volt, and
again continue it to the central contact of a lo-way voltmeter switch, to
the other points of which are attached the free ends of the other
10 wires. If, now, the voltmeter dial has been graduated to read o — 100
amperes then, with the switch on stop No. i, the voltmeter reads

900 TAYLOR: NETWORK TESTS: DISCUSSION. [Birmingham,

Mr. Taylor. 1° := o'l ampere ; and with it on No. lo it reads i° — i*o ampere, and
so far any intermediate value proportionally.

If the plate resistance = o*o2 ohm then, when lo amperes traverse
it, the voltmeter will read zero when the switch is on stop No. i ;
if loo amperes traverse it the voltmeter will read zero when the switch
is on stop No. lo, and so proportionately for intermediate values.

Take, for an example, the case where the normal out-of-balance
current of the station is only lo amperes.

Set the switch on stop No. i and the voltmeter — which is graduated,
as before stated, in amperes — will read zero. Now apply pressure to
the neutral leak (in the manner indicated in reply to Mr. Russell), and
the increment of current through the neutral feeders, due to the neutral
leak, is read directly on the voltmeter, remembering that the dial
reading in ampere must be in this case divided by lo.

If loo amperes had been the normal out-of-balance current of the
station, instead of lo amperes, we should have put the switch on to
stop No. lo, and have read the leak current direct in amperes.

It is not necessary that the reading should be at zero to begin with ;
all that is necessary is to take the difference of the two readingb
obtained before and after putting pressure on the neutral leak.

In conclusion, I wish to thank the various gentlemen who have
taken part in the discussion for the kind way in which they have
received the paper.

1903.] 901

MANCHESTER LOCAL SECTION.

THE ARRANGEMENT AND CONTROL OF LONG-
DISTANCE TRANSMISSION LINES.

By E. W. Cowan, Member, and L. Andrews, Member.

(Paper read at Meeting of Section j March 3, 1903.)

It is proposed in this paper, after a general review of the points
involved, to deal more fully with the regulation and protection of the
lines by making certain suggestions with a view to the more certain
maintenance of an efficient service ; and especially with some of the
conditions to which long transmission lines at comparatively high
pressures are subject, whether underground or overhead.

General Considerations.

Pressure. — The maximum pressure, so far as we are aware, which
has been actually in practical operation is 80,000 volts. The Standard
Co. of America have operated on one of their lines for two hours
in adverse weather at this pressure without any trouble arising. There
is no reason why this should be the limit of pressure, as transformers
have been worked well above 100,000 volts, and with liberal spacing
of the overhead wires the electrostatic leakage can be sufficiently
reduced. The capacity current increasing with the pressure must
of course be reckoned with, and, if necessary, compensated for by
suitable reactance coils in the way referred to later on. It is with
large powers and long lines that economy requires the adoption of
these great pressures. It has been contended that pressures above
10,000 volts will not serve any useful purpose in this country. We think
that these expressions of opinion indicate a narrow view of the future
development of electrical power. The essence of electricity supply
lies in its distribution, and any factor which increases the distance,
the economy, and the facility with which electrical energy can be
transmitted greatly widens the field of its usefulness. We are not
speaking of small powers, our ideas of " bulk " embracing more than
a few thousand kilowatts ; we are thinking of the requirements of the
power user and of the necessity for concentration of large units at the
centres of supply if advantage is to be taken of the use of gas fuel.
Cheapening the outside works and reducing the losses of transmission,
which is the result of the use of high pressures, greatly facilitates the
exploitation of the area suppUed. According to the development of
demand other centres of supply can be installed, the raising of the
necessary capital being then greatly simplified, not to say cheapened.
We should point out that the extra outlay involved in the use of high
pressures is trifling ; it only affects insulation of line and transformers.

902 COWAN AND ANDREWS: CONTROL OF [Manchester,

There is no reason why a scheme should not provide for the supply
being transmitted at a low pressure in the early stages of its career,
and when the requirements of the situation justified it, the pressure
could be raised merely by an alteration to the step-up and step-down
transformer connections. According to Mr. Parshall, 20,000 volts may
be taken as the safe limit for underground cables ; the cost of
insulation and the capacity of the underground cable rendering the
use of higher pressures prohibitive. There is a point in favour of
high voltage for underground cables which should be borne in mind.
Assuming the same energy transmitted by a cable, the heat energ>'
developed at a fault is, from one point of view, inversely proportional
to the square of the pressure. We consider, therefore, that the Board
of Trade should allow greater energy to be transmitted by a cable
with greater pressures.

Periodicity. — ^After much fluctuation the practice of to-day seems
to be steadying down to a frequency of 50 to 60 for alternating currents.
The Pacific Coast lines in California have adopted comparatively high
frequencies — the Niagara Company standing almost alone with its low
periodicity. It is interesting to note that out of seventy-three power
transmission installations, thirty operate at a frequency of 60 cycles
or over, and twenty-eight at between 50 and 60 cycles. It must be
remembered that the higher frequency increases the charging current,
the impedance drop, and is not so well adapted to motors or rotarics
as the lower frequencies ; at the same time lighting becomes practicable
and the transformers are cheaper.

Lightning. — It is necessary in some countries to make very elaborate
protection against lightning discharges. Atmospheric difference of
potential can best be provided against by stapling a barbed wire to
the poles and frequently earthing. The increase in capacity in the
cables due to this wire is said to be not appreciable. Disruptive
discharges are dealt with by lightning arrestors, of which there arc
many designs. The essence of nearly all types is the provision of
a small inductance (kicking coil) on the generator side of the earth
connection, in series with which the discharge part of the arrestor
is placed. A large number of spark-gaps in series with a non-
inductive resistance form the essential features of this part of the
apparatus. For reasons stated later on horn break lightning arrestors
should be avoided.

Earthing. — There is considerable difference of opinion as to the
advantages and disadvantages of earthing the neutral point in a
polyphase system of distribution. It appears to us that the advantages
of earthing are considerable. In an unearthed system the static
capacity between wire and earth with high pressures becomes a source
of danger, and this static capacity may be 83 per cent, higher than
it can possibly be if the neutral of a three-phase system be earthed.
When the neutral is earthed faults are immediately detected, and must
be removed. On the whole, the voltage available in case of accidental
contact tends to be reduced by earthing the neutral point. We learn
that the Lancashire and Yorkshire Company in their electric railway
scheme are earthing the neutral point, and thereby making an

1908.] LONG-DISTANCE TRANSMISSION LINES. 90d

appreciable saving in its cost, which is another advantage of great
consequence. The Cable Makers' Association have recently stand*
ardised a reduction of dielectric thickness between conductors and
earth of approximately one-third when the neutral is earthed.

Capacity.

The charging current required for long lines even when fixed
overhead is very large. A loo-mile line working at about 50,000 volts
and with a periodicity of 50 requires a charging current exceeding 2,000
kilo-volt-amps. This is equivalent to the full current load of a 2,600
E.H.P. plant. Unless the capacity is neutralised by reactive coils it
becomes uncommercial to transmit powers at this pressure of less than
3,000 kilowatts. The use of high potential reactive coils, which are
made preferably without an iron core, and placed as a shunt across the
mains at suitable positions on the line, is a rather expensive expedient
and also involves the introduction of many points of possible breakdown
of insulation which are better avoided. Further these coils should be
disconnected as the load comes on. The charging current on under-
ground cables is of course much greater than on overhead. The
Deptford cables at 10,000 volts take a charging current, we believe, of
45 amps. = 450 kilo-volt-amps. Large synchronous motors on the line
with their field strength suitably adjusted can be arranged to neutralise
the capacity of the cable, but their field strength must be varied with
the load on the line. An ideal arrangement would be to balance the
constant, self-induction by constant capacity and the variable self-
induction by variable leading load.

Though this capacity ciu*rent, being expended reversibly, does not
represent proportionate loss in watts, it does involve considerable loss
at light loads and also results in bad regulation, the leading current
causing an alteration in the ratios of the transformers and in the field
excitation of the generators. It should be noted that the current
required to charge cables is greater when the current curve departs
from sine form, and it has been stated that the charging current may be
increased from 200 to 300 per cent, when the waves are jagged. As
the load increases the power-factor also increases. In one installation,
having very large capacity in the cables which we were connected
with, the power-factor at full load was over 99 per cent. It is often
said that capacity is an advantage in supplying the magnetising current
for the transformers and for neutralising the self-induction of the line.
This is true, but large capacity is nevertheless the cause of far more
trouble than it saves. The Manchester 6,500-volt cables have a capacity
of 0*23 mfd. per mile between one core and the other two.

Loss in line, — The loss in the conductors must of course be worked
out for the greatest economy in each case, with due regard to the spirit
of Kelvin's Law. In long lines the loss may be as much as 50 per cent.
One hundred amperes is about the limit which can be transmitted on
one line from 100 to 200 miles long, owing to inductive drop which, with
a 200-nule line at 60 cycles and 50,000 volts, may amount to no less than
50 per cent. The necessity for high pressures to reduce the current
Vol. 82. 59

904 COWAN AND ANDREWS: CONTROL OF [Manchester,

upon which the inductive loss per mile depends, becomes, therefore,
very evident when the length of the line is great.

Overhead and Underground Conductors.

For long distances underground cables are inadmissible, not only on
account of their cost, but also because their capacity with the high
pressures necessary results in an impracticably large condenser
current. It has been very clearly shown by .our Chairman, Mr. Elarle,
and also by Mr. Stewart, that a point is soon reached at which the cost
of insulation is so high in proportion to the cost of copper in under-
ground mains, that no economy results in transmitting energy at a
higher pressure than a certain critical ascertained " cheapest " pressure.
But this '* cheapest " pressure will be further reduced by taking into
consideration the reduction of charging current which will result from
a lower pressure. The saving will be effected under the following
heads : — (i) Reduced dielectric loss in cable ; (2) charging current CR
losses in copper of cable, transformers and generator ; (3) standing
losses in light-load engine which must be larger the greater the
charging current. Proper value must be given to various factors, such
as the hours of light load (charging current is practically eliminated at
full load), reduction of condenser current due to inductive load, etc.
We have worked out the capacity current at a frequency of 50 from
data obtained from a length of vulcanised rubber concentric (37/15),
and find that the charging current at 30,750 volts on a single 27ir-mile
length of such cable with the outer earthed would amount to over 4,000
apparent kw. It will be at once seen that no possible distribution
could be carried out on these lines.

It appears to us that long-distance transmission lines should always
be run overhead when crossing open country. Mr. Earle has calculated
that the cost may be about one-third of the cost of laying the cables
underground, but in addition to the saving in cost, there is the accessi-
bility and ease of repair, and the possibility of using more economical
pressures with the greater economy in running at light loads owing to
the greatly reduced capacity current.

Against the use of overhead wires there are three objections : —

(i) Danger.

(2) Unsightliness.

(3) The Board of Trade ?

On the question of danger we do not think that serious consideration
need be given to the risk of accident from falling wires. There is a
small risk, but with a well-engineered line it is very small, compared
with many other risks which the community must and do submit to in
the general interest. Kite-flying in the neighbourhood of high-potential
lines on a wet day would become a dangerous form of amusement, and
ballooning would also prove an exciting sport. There is no doubt that
if an air-ship became entangled with a 50,000-volt line it would suffer
rapid deterioration.

1903.] LONG-blStANCE tRANSMISSIOX LINES. 905

On the question of appearance, these lines would not look worse,
but rather better, than existing telegraph and telephone lines.

Finally, there is the Board of Trade. In their letter some time ago
to the Chairman of the London Chamber of Commerce the Board of
Trade intimated that they were prepared to consider overhead schemes.
We therefore consider that there is a fair prospect of obtaining consent
to a form of distribution which can be, we think, readily proved to open
out much greater possibilities in the direction of cheap power, which
means cheaper production and consequently greater prosperity in the
country.

Overhead Construction.

Poles and Conductors, — The poles are generally of wood from 35 to
40 feet in length, and spaced about 50 to the mile. In some instances
steel towers are being used which get over the difficulty of the decay
which takes place in the part of the pole underground. The steel
towers in the case of one 60,000-volt installation in Mexico are placed
440 ft. apart. It has been stated that the cost of these towers does not
exceed that of a first-class pole line. As an instance of what can be
done, there is a single span of 4,000 ft. on the Bay Counties Co.'s line in
California. The insulators are made of glass, vitrified porcelain, and of
brownware. The latter are said to be less alluring to the sporting
instinct, and the glass insulators have an advantage in their trans-
parency, annoying the spiders which prefer to spin their nests in the
dark. Porcelain must be thoroughly vitrified. A f in. slab of unvitrified
porcelain punctured at 17,000 volts under test, whereas a piece of well
vitrified porcelain i in. thick withstood 49,500 volts. The insulators
for high pressures are generally made with three petticoats. For such
pressures as 60,000 volts they will be about 14 in. in diameter, and placed
about 10 feet apart. For 30,000 volts they will be about 7 in. diameter.
Aluminium wires have been used in some cases, notably by the
Standard Company in America. The weight of these conductors for
the same conductivity is about half that of copper, the strength about J,
and the diameter 30 per cent, greater. The question of durability can
only be settled by time, but the lighter weight enables the spacing of
the poles to be increased or the safety factor to be higher. An
incidental advantage electrically is that the electrostatic leakage is less
with aluminium cable, as its surface is larger.

Electrostatic Leakage, — The electrostatic leakage, taking the form of a
brush discharge between wires, with high pressures is considerable,
and the use of conductors of less diameter than i in. becomes
prohibitive.

A test on an actual line showed loss of energy due to air leakage
with 47,300 volts to be 1,215 watts per mile when the distance between
the wires was 15 inches. When this distance was increased to 52
inches the leakage was reduced to 122 watts per mile. With high
pressures it is usual to place the wires about 10 feet apart.

Inductive Drop. — Self-induction and mutual induction must be
taken into consideration, and on long lines both may have considerable

D06 COWAf^ And ANDREWS: CONTROL OI^ [Manchestci^ ,

effect. Mutual induction can be neutralised to a large extent by
suitable transposition of the wires, each case being worked out
according to the circumstances. In the instance of two overhead
three-phase S3rstems, the mains of each system should be spiralled, the
pitch of the one being three times that of the other. The mutual
induction will then be zero. The drop due to self-induction is
compensated for to some extent by the capacity of the line.

Electrostatic Induction, — ^This form of induction affects neighbouring
telephone lines and may make them unworkable. It is not easily
dealt with, and such lines should give each other a wide berth in order
to avoid trouble.

Underground Line Construction.

Underground cables are all but universally used at the [^resent
time in this country for the distribution of electrical energy, excepting
the trolley lines for electric traction. The system which has found
most favour is the so-called "solid system." A typical method of
laying has been adopted in Manchester, where the high-pressure
conductors are laid in cast-iron troughs filled with bitumen. The
figures and curves relating to cost given in Mr. Earle's paper, before
referred to, must he corrected, owing to the fact that they were based
upon a thickness of insulation which it was assumed the Board of
Trade insisted upon. It has since been ascertained that the regulation
of T^th in. thickness of insulation per i,ooo volts does not apply to
the cxtra-high-pressure cables, and that each case will be considered
on its own merits. One cable maker informs us that he is of opinion
that i inch radial depth of dielectric is sufficient to withstand 6o,qoo
volts pressure, but he is unable to say whether the insulation would
withstand such a stress for any great length of time. The Cable
Makers' Association have recently standardised a thickness of little
over t inch for 10,000 volts working pressure.

We now pass to the second part of our paper, dealing^ with
Regulation and Protection of High Pressure Lines.

In 1896 one of the authors of this paper, in conjunction with Mr. A.
Still, submitted a communication to the Northern Society c^ Electrical
Engineers, a section of which dealt with feeder regulation with
static boosters. Since that date certain improvements have been
made in the variable induction type of regulating transfcM-mer,
whereby its inductance and magnetising current have been substantially
reduced. In the discussion on the paper referred to, Mr. Rider, Mr.
Mordey, and others expressed the opinion that the system recommended
was the best method of regulating. Briefly this system, which has
been widely adopted, consists in connecting the feeder in series with
the secondary of a transformer, the pressure across which can be
varied by operating a hand wheel. In supply works where there is
only one transmission line such apparatus is not needed, as the 'bus-bar
pressure can readily be varied ; but in cases where there are two or
more transmission lines of different length or load, independent
regulation of each line is necessary. There is practically no loss in

1903.]

LONG-DISTANCE TRANSMISSION LINES.

907

efficiency in augmenting the pressure on a line in this way, the losses
in the booster being sometimes less than the saving in supplying the
'bos-bars at a lower pressure. This js owing to the core losses in the

P05ITE0N OF ZLRO
SLCONDARV pressure:

Fig. I.

SECONDARy PRESSURE

Fig. 2.

generators varying approximately as the square of the induction. The
mass of iron in generators will, of course, greatly exceed the iron in
the boosters.

Figs, I and 2 show the winding and arrangement of core of the

908 COWAN AND ANDREWS: CONTROL OF [Manchester

improved Variable Induction Transformer, in the position of zero
secondary pressure. Instead of the secondary winding being wound
entirely upon the ring, it is wound half on the movable core and half
on the ring. The primary winding is wound as before on the movable
core. The result of this arrangement is that the magnetic lines
induced by the primary winding cut the half of the secondary wound
on the movable core in a positive sense, and the half of the secondary
on the ring in a negative sense in the relative position shown in Fig. i.
The resultant E.M.F. in the secondary is therefore nil. In Fig. 2,
however, the movable core has been rotated through an angle of 180°,
and the magnetic lines cut both the secondary windings in a positive
sense, the resultant E.M.F. being the sum of the two, and therefore a
maximum. In intermediate positions, intermediate secondary pressures
are obtained.

It will be at once seen that there is practically no magnetic leakage
between the primary winding and the half of the secondary winding
on the movable core, and that the number of secondary turns on the
iron ring being half of the total, the tendency for magnetic leakage
to occur at the air-gap is proportionately reduced. The result is that
there is only a total drop of six to seven per cent, on the secondary
between no load and full load.

A further improvement consists in fixing shading coils on the
movable core in the positions shown, and marked s c in the diagram.
These shading coils neutralise the inductance of the secondary circuit
when the movable core is in intermediate positions.

Lastly, the slots in the ring which contain the secondary coils are
so placed that the area of gap between movable core and ring is as
large and as equal as possible in all positions, thereby keeping the
magnetising current as low and as constant as possible.

The result of these improvements has been to bring the apparatus
up to a standard which leaves very little room for further improvement

Before describing certain special apparatus for the protection of
transmission lines, we have thought it worth while to discuss the
dangers to which such lines may be subjected under working con-
ditions : —

Abnormal Pressure Rise in Transmission Circuits.

A great deal has been written upon the subject of rises of pressure
which take place under certain conditions in long circuits having
considerable self-induction and capacity. Mathematicians have figured
on the subject at length, and experimentalists have reproduced many
of the phenomena accompanying line disturbances. At the same time
the subject is enveloped in a certain amount of mystery, and cannot
be considered as fully understood. It is usual for engineers to speak
glibly of resonance and capacity effects, and they understand the effect
of the equivalent of the inertia of the current in the shape of self-
induction. It is generally appreciated that all three of these influencing
factors combined in certain relations are responsible for the truly
terrible rises of pressure which sometimes unexpectedly occur,

1903.] LONG-DISTANCE TRANSMISSION LINES. 909

It is important that engineers should understand as far as possible
the physics of these phenomena, and we have therefore dealt rather
fully with the question, in the hope that, to a small extent, what we
have written, and, to a large extent, the criticisms which we trust will
follow from other engineers may tend to the elucidation of some of
the mystery. In the first place, the rises of pressure are beyond
question great in destructive effect. We have experienced them
ourselves many times. In one case the opening of a switch on load
caused the instantaneous breakdown of four transformers, and an
alternator armature to flash to its field poles. In another case the
rupture of a fuse in a sub-station caused the most violent rise of
pressure at the transmitting end of the line, explosively destroying an
electrostatic voltmeter and doing other damage. A transformer at
Hastings broke down, and presumably was the cause of the simultaneous
breakdown of another transformer, connected to it . only through the
station 'bus-bar by a three-mile length of conductor. On the Altrincham
circuits it used to be a regular custom to examine the fuses in all
transformers within a certain radius of any one transformer in which
they had blown, and it was often found that a number of fuses had
blown simultaneously. At the Paris Exhibition a man drove a nail
into a cable, and it was simultaneously punctured at a point a mile
distant A rise of pressure of ^ to i a million volts has been observed
on a half-mile H.T. cable with considerable self-induction when the
circuit was broken, the normal pressure being only 10,000 volts.

Passing over the opening of circuits of large self-induction per sc,
such as field coils, etc., we will first consider the case of opening a
circuit having self-induction and also capacity to an appreciable extent.
In this case the capacity takes the place of the arc formed at the switch
or fuse break as the equivalent of a relief valve tending to reduce the
rise of pressure, and at first sight it might be thought that the presence
of capacity was just what was wanted. Indeed, it has been pointed
out again and again that underground cables having necessarily more
capacity than overhead, are freed thereby from such severe rises of
pressures. But the arc, when steady and maintained, is a far more
efficient relief to the line than capacity. In the arc the electro-
magnetic energy stored in the cable is discharged through resistance,
and thereby doing work, is dissipated. But if capacity exists, the arc
is abruptly extinguished owing to the rise of pressure sufficient to
maintain it being checked by the flow of current into the condenser.
The full amount of electro-magnetic energy stored in the cable will
therefore be converted into electrostatic energy in the condenser. At
the moment the cable was opened the condenser was charged by the
normal pressure of the circuit, so that the charge it receives from the
electro-magnetic energy of the line will, according to its measure,
increase its pressure. It is easy to calculate what this rise of pressure
will be if the data be given. But that is not all, the condenser differs
from the arc in that it does not dissipate the energy put into it, but
instantly returns it to the circuit to be reconverted into electro-magnetic
energy. The process is then reversed again, and an oscillation set up
between the electrostatic and electro-magnetic state at a rate depending

910 COWAN AND ANDREWS: CONTROL OF [Manchester.

upon the natural period of oscillation of the circuit which will be slower
the longer the circuit may be. The frequency will in all cases be very
much higher than the normal frequency of the supply to the circnit.
It has been shown that under certain conditions a pressure rise in volts
may occur of txvo hundred times the interrupted current in amperes, and
these conditions are such as may occur on commercial transmission
lines.

It thus appears that to draw out a long arc at the switch contacts is
the safest way of opening a circuit of high inductance, and in our
opinion with continuous currents this is the best practice. With
alternating currents, however, a new disturbing factor is introduced by
the open-air arc. It is well known that an arc between carbons will
emit a musical note if it be shunted by a condenser and arranged in
series with a very small amount of self induction, such as will be
obtained from the conducting leads or a coil of wire. This musical
note is due to the arc being intermittent, and the rapidity of these
interruptions may, at any rate in the case of an alternating-current arc,
be very great — 3,000 to 4,000 per second. Here then are all the condi-
tions which are well known as the cause of pressure rise. In an
induction coil or transformer the induced pressure increases propor-
tionately to the frequency of intermittence of current or of alternation
when the induction in the core is constant.

The intermittent arc at switch break has been compared to the
Wehnelt Interrupter, the self-induction and electrolytic polarisation of
the latter being replaced by the self-induction and capacity of the
former. In one installation we have been associated with, the capacity
of the mains was no less than 87*8 microfarads. It is not difficult to
get some idea of the volcanic conditions of a circuit under such condi-
tions, the roaring arc at switch or fuse kicking waves of E.M.P. into the
circuit, which are met by surging waves of varying periodicity, travelling
about the cables and their branches at a speed something less than that
of light, causing resonant effects where their crests coincide and rises
of pressure at every terminal point and every point where there is a
change to greater inductance and less capacity. Such a storm of
colliding E.M.F.'s will break down the insulation of any system. Arcs
have been drawn out to a length of 35 feet under such conditions with
40,000 impressed volts and 150,000 volts pressure observed while the
arc was flaring. We have no room on modem switchboards for arcs
35 feet in length, and to use an open break switch on high-potential
circuits having appreciable self-induction and capacity is bad engineer-
ing. We may mention here that metal arcs are much worse than
carbon, the conducting vapour of the latter tending to prevent the
intermittent extinction of the arc. Soft carbon break would be the
safest, and there is an open field for switch designers to construct an
air break switch, the arc of which shall be maintained at gradual
increasing resistance, and the first break in which must be the last. A
low resistance intermittent arc is the worst of all for producing the
above effects.

On all high-potential alternating-current circuits the oil break switch
is being generally adopted at the present time. But an oil break switch.

1908.] LONG-DISTANCE TRANSMISSION LINES. 911

though it prevents the formation* of the dangerous intermittent arc,
appears to be an unscientific method of opening any circuit with appre-
ciable self-induction. The self-induction of the circuit being the same,
it seems to us to be equally bad to open an alternating*current as to
open a continuous-current circuit abruptly, whether under oil or by
magnetic blow-out. It is true that there are many chances against
opening the alternating current at its mean value, but at the same time,
are there not some chances that it will open at the wave crest which is,
with a sine curve, 41 per cent, higher than the mean ? We are unable
to see any physical difference between the suddenly opened alternating-
current and the continuous-current circuit in respect to rise of pressure
due to the accumulated electro-magnetic energy with which the circuit
is linked if the current is the same in each case. At the same time, if
it can be shown that the oil break switch always opens the circuit at a
point in the current wave much below the mean, our objection would
be withdrawn. We do not in any case contend that the oil break
switch is not the best form for engineers to adopt at the present time
for very high pressure circuits which must be opened under load,
though water break is safer in cases where space can be afforded.
We have dealt with the most important results of current surging
first, but there are other causes of rises of pressure which must be borne
in mind. There may be a resonant rise of pressure, especially if the
curve of E.M.F.and current departs much from true sine form. These
rises, which are steady when the cause is steady, are due to interference
between the generator waves and the waves of oscillation in the cable.
It can only take place when there is capacity and self-induction, but
may be set up by the fundamental waves of the generator or by odd
multiple harmonics or overtones thereof. Resonant effects have been
observed with continuous currents owing to slight waves being
generated by the commutator. Rotaries have been known to produce
resonance, their commutators being again the cause. The general
result, however, of steady resonance is not serious, and the rise in
step-up transformers due to the leadmg current will in general be many
times greater than that due to resonance. Regulation is not easy
when resonance occurs only at some critical speed.

While the opening of a circuit under load is the worst condition for
causing rises of pressure, rises will also occur when an unloaded line
is opened or closed. According to many authorities on this subject the
rise cannot exceed double the normal pressure under these conditions,
and it is easy to follow the reasoning on which this conclusion is based.
When the switch on a "dead" circuit is closed, the electrostatic energy
stored in the cable may be equal to or greater than the electro-magnetic
energy stored in the ether surrounding the cable by the current flowing
to charge it. This latter energy will be converted into electrostatic
when the impressed E.M.F. of the circuit equals the back E.M.F. of
the condenser, the result being that a double quantity of electricity can
be forced into the condenser, and the final pressure may consequently
be double the normal. In the same way opening an unloaded circuit
may result in a rise of E.M.F. double the normal pressure. As a matter
of fact, however, a higher pressure than double the normal has been

912 COWAN AND ANDREWS: CONTROL OF [Manchester,

recorded when closing the switch of an unloaded line of 44 miles in
length. This increased rise is probably due to some coincidence
between the crests of the impressed waves of E.M.F. and the crests of
the waves of E.M.F. of high frequency, which accompany the natural
oscillations in the cable.

Reviewing the whole question, one is forced to the conclusion
that circuits having appreciable capacity and self-induction should
not be switched on or off, whether loaded or unloaded, suddenly.
All surging currents should be avoided, and fuses should be used only
when the natural reactance of the circuit is too small to prevent a
dangerous rise of current.

In the next section of our paper we describe various methods of
switching currents on and off gradually, which have been devised to
prevent the system from being submitted to dangerous pressures.

Cable-charging Apparatus.

The earliest cable-charging apparatus of which we have any know-
ledge is that installed at Deptford, Willesden, and in other places. It
has been described before, and we will, therefore, only briefly refer to
it now. It consists essentially in closing the circuit through high
inductance, which inductance is gradually removed by manipulating a
liquid resistance in series with a secondary winding on the inductance
coil. An ordinary transformer can be used. Mr. G. W. Partridge
informs us that it is important with this apparatus to short-circuit the
primary winding as soon as the full E.M.F. is indicated by the circuit
voltmeter. If this is not done, he has found that a rise of pressure
50 per cent, above the normal may occur on the circuit. This is.
probably due to the circuit reaching the condition of resonance. This
arrangement has recentiy been objected to on account of the probability
of resonant rise of pressure occurring with it, but it seems to us that
as the pressure of the circuit is under observation when the apparatus
is being used the danger is small. The fact that this apparatus has
been in daily use at Deptford since 1892, and Mr. Partridge informs us
is working perfectly satisfactorily, is, we think, good reason for regard-
ing it with confidence.

Another method of charging is to run up a separate motor alternator
on the circuit, and then to synchronise and parallel. The chief
objection to this system is the time it takes to perform the operation,
and the apparatus must also be somewliat complicated and costly. This
system is in use in Manchester and elsewhere.

A third method is one which one of the authors worked out some
years ago. It consists in using a regulating transformer of the type
described in the section of this paper dealing with '* Regulation."
The secondary is wound to give the full E.M.F. of the circuit when the
movable core is in the position of maximum effect, and the primary
is excited from the main 'bus-bars. Fig. 3 shows the arrange-
ment of connections for single-phase working. The system is equally
applicable to the polyphase supply. In the figure, A, and A, are the
'bus-bars, R is the regulating transformer, C is the circuit, and B3 is the

1903.]

LONG-DISTANCE TRANSMISSION LINES.

913

charging 'bus-bar. When it is desired to charge a circuit, it is
plugged on to the charging bar by means of the plug P. The regula-
ting transformer is then operated by a hand-wheel until its secondary
volts equal the main *bus-bar volts. The main switch is then closed,
and the plug withdrawn. The whole operation can be effected in a
few seconds, and it has the advantage of t>eing reversible, that is to say,
circuits can be gradually switched off as well as gradually switched on.
It occupies a very small space, only one transformer being required for
any number of circuits. As the transformer is only excited for a very
short time it is safe to work at a high induction in the iron and a large
current density in the copper. Messrs. Cowans have used a standard
15 kw. regulating transformer (Fig. 4) for 150 kw. charging current,
the temperature rise being inappreciable after five minutes at full
load. They have also been made to give, in conjunction with a step-up
transformer, 60,000 volts secondary pressure.

sr^

>''

/»«

-♦

ss^**

COWAN STILL.

CABLE CHARCINC

Fig. 3.

C
SYSTEM

The last arrangement for cable-charging we propose to describe is
a variable water resistance method. The system has been recently
worked out by Messrs. Ferranti, and the apparatus is illustrated in
Fig. 5.

It consists of a metal containing vessel A supported in a cast-iron
case B, on and by insulators C*, C, C\ In the containing vessel are
rigidly fixed two porcelain tubes D», D", these tubes being about
5 feet long by 3 inches internal diameter. Each tube contains an
ebonised iron rod E, carried at its upper extremity by an insulator D.
At the lower end of this rod is a piston F, upon which is fixed a metal
cap G. This cap is electrically connected to the terminal H by a
spiral tape conductor I. The piston F fits into a well at the bottom of
the containing vessel, which is filled with mercury. A gauge glass J
enables the height of the water to be seen through a glass window in
the outer case. The height of this water is normally kept about 3 feet
above the bottom of the containing vessel, and the total upward travel
pf the rods is 2 ft. 10 in. The apparatus illustrated is intended for use

914

COWAN AND ANDREWS: CONTROL OF [Manchester,

in connection with a two-phase system, one tank being provided for
each phase. The ebonised rods are carried at the extremities of a
connecting crosshead. The weights K tend to lift the crosshead, but
this is prevented when the rods are in the lowest position by a catch
controlled by an electric magnet L.

The method in which this charging gear is inserted in circuit with
the feeders is practically similar to that shown in Fig. 2. To charge
a feeder the catch is released, thus allowing the balance wei^ts
to lift the crosshead and so increase the length of the column

±=R

0,*

h" \

! I

1 r

Fig. 5.

of water to its maximum. The feeder switch is set at half-cock,
thereby connecting the feeder to a small auxiliary 'bus-bar corre-
sponding to the synchroniser bar in the " Ferranti " standard generator
switch-gear. This bar is connected to one terminal of the cable-
charging device. The other terminal is connected to the main
'bus-bar through a fuse and switch on a special feeder-charging-
panel. The water resistance in series with the feeder is then
gradually reduced by pushing down the crosshead to its extreme limit
of travel. This is done by a length of rod terminating in a handle
above the switchboard gallery. When all the resistance has been cut
out the catch comes into operation and holds the crosshead down ; the
feeder switch is then finally closed. A hand release to the catch is
provided to enable the apparatus to be used for charging another cable
in a similar manner. To discharge a feeder the rods are pushed down

Fig. 4.

1903.]

LONG-DISTANCE TRANSMISSION LINES.

915

to their lowest position (if they have not previously been left thus), and
the feeder switch is pulled out on to the second contact. In this
position the magnetic release trips the catch and thus allows the weight
to descend and gradually increase the length of the column of water.
The operation is finally completed by opening the oil break switches on
the feeder charging panel. A plug switch is provided for isolating
purposes only.

Duplication of Transmission Lines.

Without question every high-potential line should be duplicated.
The Board of Trade in general insists "upon this being done. These

Fig. 6

Fig. 7.

duplicate lines should be run in separate ducts if laid underground,
and on separate poles if overhead. It is not safe to work on a high-
potential line while any of the wires on the cross arms are alive.

Some engineers have held the view that to ensure continuity of
supply one of the lines should be kept as a spare — ^that is to say, the
duplicate line should not be coupled in parallel.

When it is remembered that the line losses are proportional to the
square 0/ the current^ it will be clear that the losses in transmission will

916 COWAN AND ANDREWS: CONTROL OK [Manchester,

be four times as great if the spare main is kept idle. It will be evident,
therefore, that the difficulties arising through coupling the mains in
parallel must be very serious to induce engineers to increase their line
losses fourfold rather than face these difficulties. A system cannot be
considered efficiently duplicated unless arrangements are made for
reliably disconnecting the short-circuited feeder from the system,
leaving the supply maintained through the healthy feeder. Many
attempts have been made to do this by inserting fuses at each end of
both of the feeders. These fuses should evidently all be of the same
capacity, as it cannot be foreseen that any one of these will be required
to carry more or less than the pther. Now, should a fault occur at E',
Fig. 6, fuse A will certainly be blown first. Current will then feed
back through fuses B, C, D, but B, C have now to carry the whole
of the current to the load L, in addition to the current necessary to
blow the fuse D ; as a consequence, fuse B or C is almost certain to
be blown before fuse D, and a complete interruption of the supply will
occur.

This interruption would not be so serious if the attendants at the
generating station, and at the distributing centre, were able to at once
disconnect the faulty main and continue the supply through the healthy
main ; but this they cannot do because they have nothing to indicate,
without testing, which main has failed. As a consequence considerable
time must elapse before the supply can be continued. When the line
has ultimately been cleared, if synchronous motors are used in the con-
verter stations these will all have to be run up and paralleled, and after
this has been done, if all consumers have left their motors connected to
the supply, a very heavy starting current will be required to get them
away. In connection with several of the power schemes in the States
consumers have been requested to disconnect their motors whenever
an interruption to the supply occurs and to keep them off until the
supply is recommenced, and then switch them on one by one.

The loss arising through the stoppage of many hundreds of motors
for only a quarter of an hour is liable to be extremely heavy.

It is not then surprising that some engineers have considered it
advisable to keep one of their transmission lines purely as a spare, so
that the attendant at each end of the line can switch over from the
faulty main to the spare main. This can sometimes be done sufficiently
quickly to prevent any appreciable slowing down of induction motors
and rotary converters.

A perfect duplicate transmission line should, we think, fulfil the
following specification :—

(a) It should be possible, without increasing the risk of an in-
terruption to the supply, to keep both lines in continual
service, thereby reducing the line losses by 75 per cent.
(6) A fault on either line should have no effect on the remaining
line, other than causing it to carry the whole load pre-
viously borne by the two.
(c) The supply to the distributing centre should not be even
momentarily interrupted, as the shortest interruption is
sufficient to cause synchronous motors to fall out of step.

1903.] LONG-DISTAXCE TRANSMISSION LINES. 017

A system devised some years ago by one of the authors ^hich is in
use in this country and in the States is to place return current, or dis-
criminating cut-outs, at the distributing end of the transmission lines in
place of the fuses C and D, Fig. 6.

This system meets the requirements of the case for high-resistance
faults, but difficulties occur with low-resistance alternating-current
faults.

Another defect which the above arrangement shares with a system
protected by fuses alone is that immediately the fuse on the power-
station side of the fault has blown, the whole of the current to the short
will be thrown upon the healthy main, and A{ the cut-out or fuse at
the distributing end of the faulty main operates, when it will be re-
quired to break this heavy short-circuit current with consequent line
disturbance.

A simple device for the protection of duplicate mains is illustrated
in Fig. 7.

It will be seen that the feeders are connected together at the dis-
tributing end by a choking coil, wound entirely in one direction. The
supply to the load is taken off from the centre of this coil.

Under normal conditions, the current divides equally between the
two feeders and the two halves of the choking coil, but the current from
one feeder flows round the iron in one direction, and from the other
feeder in the opposite direction, and as a consequence the winding is
perfectly non-inductive, and the only resistance to the flow of current
is that due to the ohmic resistance of the circuit.

Should a fault now occur at say E' the fuse B will be blown, and the
current will tend to feed back towards the short through the choking
coil at the distributing end of the lines. This current will, however, be
entirely in one direction, and the choking coil will, in consequence,
become a highly inductive resistance, and will prevent a heavy current
flowing to the short The supply will not be even momentarily inter-
rupted, but it will be maintained at half-pressure only, so long as the
faulty main is connected to one side of the choking coil. The attendant
in the distributing station will, however, be able to instantly see from
the instruments which feeder has broken down, and no time need be
lost in switching this off and leaving the supply maintained through the
healthy feeder alone.

It will be evident that when one feeder only is left connected, the
choking coil must either be short-circuited or must be so connected up
to the one main as to cause the current to divide equally between its
two halves. The simple two-way switch shown in Fig. 7 may be
used for this purpose.

No automatic cut-outs of any description are necessary with this
device, as even if the attendant is not at hand to instantly operate the
switches no further damage will result to the system, and the supply
will be maintained at half-pressure. If, however, it were possible to
automatically operate the two-way switch at the distributing end of the
lines there would certainly be some advantage in doing so even in cases
where an attendant is normally in charge, and for small sub-stations in
which there are no attendants, some automatic device would certainly

918

COWAN AND ANDREWS: CONTROL OF [Mancheeter,

make the arrangement more complete. It is beUeved that the automatic
release shown in Fig. 8 will prove to be perfectly reliable, and
it is so simple and free from delicate and moving parts that it appears
scarcely possible that it should get out of order.

Two small transformers are connected up as shown in the diagram
between the two high-tension feeders. Under normal conditions the
direction of the current in these windings will be as indicated by the
arrow-heads ; and this magnetising force will tend to cause a flux to

mmmJ

Fig. 8.

circulate round the outer limbs of the transformer. There will obviously
be no tendency for magnetic flux to flow through the centre limb upon
which the secondary winding connected across the copper fuse wire
supporting the weighted switch is wound. Should, however, one oi the
feeders break down, the two small transformers will be fed from the
remaining healthy main only, and the direction of the current and
resulting flux will be as shown in Fig. 9. It will be seen that the flux
in the transformer controlling the switch on the healthy main remains
as before, but in the other transformer the flux will be diverted through
the centre limb, and a heavy ciurent will be induced in the copper fuse
supporting the weighted switch on the faulty main, thus causing this to

1903.]

LONG-DISTANCE TRANSMISSION LINES.

919

open and instantly disconnect the fault, leaving the supply maintained
at normal pressure through the healthy main.

In Figs. 8 and 9, the controlUng transformers are connected to earth
at £, and the contacts A and B are connected respectively to the
opposite feeders.

The system described above, which has been recently shown in
practical operation to a number of engineers at Hastings, appears to us
to fulfil the three requirements specified above at a reasonable cost.

Fig. 9.

Current Direction Indicator, — A modification of the discriminating
transformer referred to above may be used with alternating-current
generators connected in parallel for the purpose of indicating whether
a generator is feeding the 'bus-bars or receiving current therefrom.
Without some device of this description the attendant has nothing to
indicate, in the event of a failure, which generator to switch out, as the
fault will cause the ammeters on both the defective machine and on the
remaining healthy machines to indicate an excess current. Serious
interruptions have resulted from this cause.

The discriminating transformer is in this case connected up as
shown in Fig. 10. Red and green lamps, A and B, are connected
Vol. 82. 60

920

COWAN AND ANDREWS: CONTROL OF [Manchester,

respectively across the terminals of two secondary windings. A
primary winding C is connected directly across the 'bus-bars or across
any secondary circuit excited from the main 'bus-bars. The effect of
this primary winding is to induce a magnetic flux in the core of the
transformer in the direction indicated by the thin arrows. A second
primary winding D consists of one or two turns inserted in series with
the generator connections. The effect of a generating current in this
winding is to induce a flux in the direction shown by the thick arrows-
It will be seen that the fluxes due to the two primaries oppose each

Fig. id.

Fig II.

other through the secondary connected to the red lamp, and assist each
other to light the green lamp. Should the generator fail, the direction
of the series flux relatively to the shunt flux will be reversed, and as a
consequence the green lamp will be extinguished and the red lamp
lighted. This current-direction indicator has also proved of great
assistance in getting machines out of parallel.

Fig. II shows the current-direction indicator fitted into the fuse
pot of a Ferranti switchboard. This forms a simple arrangement in
cases where fuses are not required in the generator panels.

We trust that the importance of the subject will be accepted as an

1903.] LONG-DISTANCE TRANSMISSION LINES : DISCUSSION. 921

excuse for the length of this paper. We are hopeful that, by co-opera-
tion between all who are interested, manufacturers, consulting engineers,
and capitalists, Great Britain may, in due course, take the position in
Long-distance Power Transmission she has held for so long in Long-
distance Telegraphy.

We wish to express our thanks to Messrs. Ferranti, Mr. F. Pooley,
Mr. W. B. Esson, and Mr. Preece, all of whom have kindly furnished
useful particulars.

Mr. H. C. GuNTON did not agree with the authors on the earthing of Mr. Gunton.
the neutral point of the three-phase system. A case had recently come
under his notice in which a man had received a shock from one of the
arms of a 6,000- volt system and had recovered from the shock. This
system was not earthed ; had it been so, undoubtedly the shock would
have proved fatal, whereas he had only received a condenser discharge.
The use of a motor-alternator for charging the feeders, and discharging
them, was found very satisfactory, and the operation could be quickly
performed. There should always be duplicate mains (feeders), but in
some cases it was not advisable that they should be run in parallel.
Where, for instance, the mains fed a sub-station from which lighting
and traction were supplied, it would be found advisable to use one
feeder for lighting and one for traction, instead of running the two in
parallel ; should one break down, the other could, of course, be used
for the whole supply. Double duplicate mains would be very
costly.

Mr. F. PooLEY thought the capital cost of some power companies Mr. Pooicy.
could be reduced by having portable transforming apparatus. For
instance, where the supply included seaside towns with a summer peak,
and manufacturing towns with a winter peak, the apparatus could be
used for the two cases. The cost of cables could be reduced if it were
taken that the dielectric did not require to be proportionately thick
with the higher voltages. He thought that the barbed wire run
parallel to the transmission Hues to overcome the effects of lightning,
as described in the paper, would increase the capacity. The length of
life of the line could be covered by a 5 per cent, depreciation fund, if
the poles were well creosoted. The cost of aluminium wires worked
out about the same as copper, but the poles could not be distanced to
any appreciably greater extent with the former.

Mr. H. W. Clothier said that the authors had dealt with several MrCiothicr.
important features of alternating-current working. He considered that
the flare switch for alternating-current working was obsolete. The
magnetic blow-out system in continuous-current working was bad,
owing to the tendency of the voltage to rise on the sudden breaking of
the circuit. A question of vital importance was that of cable charging ;
there was much obscurity, and though there were numerous calcula-
tions and theories of what happened when a high potential was
suddenly switched on or off a cable, there were few actual records of
results. In America and in several British stations no "charging"
appliances were used, and yet they had heard little of disastrous
effects. Perhaps they were paying too much attention to the subject ?

922

COWAN AND ANDREWS : CONTROL OF [Manchester,

Mr. Clothier.
Mr. Nisbett

Mr.

Coubrough.

Mr. Kemp.

Messrs.
Cowan and
Andrews.

He would like to know what were the limits before " cable charging"
became advisable.

Mr. G. H. Nisbett was sorry that the first part of the paper con-
sisted of an appreciation of overhead as against underground cables.
He thought that what was often said of overhead wires must be taken
with a grain of salt. A number of objections, more or less reasonable,
were cited against overhead mains, and he concluded that overhead
wires were a relic of barbarism. It was unfortunate that cable-makers
did not know to what stress their cables would be subjected. In one
instance, where the cables had to carry current at a pressure of 5,000
vohs, it was found they were subjected to a pressure of from 12,000 to
13,000 volts every time they were switched on or ofiE. Engineers
should specify a maximum rise of voltage, and see that this was kept
to ; also, he would emphasise the importance of the alternator curve
being as nearly a sine curve as possible. He agreed with the authors
that it was advantageous to earth the neutral point of the three-phase
system ; by this means a saving of 15 per cent, could be made on the
cost of the cables.

Mr. A. C. Coubrough noted with surprise that the authors thought
the single-phase alternating-current system could come into use again.
The only chance for that system would be by the adoption of seriesr
wound single-phase motors, and then probably a two- phase generating
system would be adopted. The only sound reason for adopting a two-
phase system was the possibility of using mains that had served for a
single-phase system. Frequencies were steadying down, 60 cycles
being now the upper limit, and the lower limits were fixed by the
requirements for satisfactory lighting ; probably ^o cycles would be
found best for all-round purposes. Generators, when taken in con-
junction with their driving motor, varied very little in cost with
different frequencies, and the advantages of smaller capacity, less
charging current and lower impedance drop, were with the lower
frequencies. Both arc and incandescent* lighting were suitable at 40
cycles. More knowledge was wanted of the various phenomena accom-
panying the disruption of high-potential alternating-currwit circuits ; h^
would suggest that a possible combination of an oscillograph and a
cinematograph camera might be useful.

Mr. J. P. Kemp did not agree with the earthing of the neutral point
of the three-phase system ; this would necessitate more insulation on the
generators, and would reduce the safety-factor of the system. Cases in
which men touched one of the arms of H.T. non-earthed three-phase com-
binations, and were not killed, were evidenced as proof of this. A method
of charging cables by means of a step-up transformer and motor alter-
nator, which had been in operation nine months, was very satisfactory.
The Board of Trade required tests to be made at i^ times the working
pressure, and the "charging" plant had been most useful in this
respect. The time taken to charge up a feeder was about forty-five
seconds.

Messrs. Cowan and Andrews replied very briefly to the points
raised. From the statements made in the discussion, Mr. Cowan was
prepared to modify his view on the earthing of the neutral point of the

1903.] LONG-DISTANCE TRANSMISSION LINES : DISCUSSION. 923

three-phase system when the pressure and condenser capacity of the Messrs.
cables were within moderately safe limits, as appeared to be the case ax^Sk^
in Manchester. There was always the danger, however, that a fault
might be allowed to remain some time unrepaired when the neutral
was not earthed, and in this case the danger was increased by not
earthing. The increased capacity due to barbed wire for protection of
transmission lines from lightning, was said to be inappreciable. He
thought the question of pressure rise in cables must be a matter for *
experiment. He was at a loss to understand why in some cases in
America the frequency had been raised instead of lowered. Mr.
Andrews thought that where a sub-station supplied current for both
lighting and traction, duplicate mains for each ^should certainly be
used.

Vol. 82. 61

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JOURNAL

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Founded 1871. Incorporated 1883.
Vol. 32, 1903. No. 163.

The Three Hundred and Ninety-fourth Ordinary General
Meeting of the Institution was held at the Society of
Arts, John Street, Adelphi, W.C., on Thursday evening,
May 7th, 1903 — Mr. Robert K. Gray, President, in
the chair.

The minutes of the Ordinary General Meeting of April 30th, 1903,
were, by permission of the meeting, taken as read, and signed by the
President.

The names of new candidates for election into the Institution were
taken as read, and it was ordered that the names be suspended in the
Library.

The following list of transfers was published as having been
approved by the Council : —

From the class of Associates to that of Associate Members —

John William Gibson. | Jas. Noel C. Holroyde.

Joseph P. McMahon.

Messrs. C. W. Barnes and R. Tervet were appointed scrutineers of
the ballot for the election of new members.

Donations to the Building Fund were announced as having been
received since the last meeting from Messrs. W. S. Entwistle and
E. M. Malek ; and to the Benevolent Fund from Mr. W. S. Entwistle,
to all of whom the thanks of the meeting were duly accorded.

The following papers were then read : —

APPLICATIONS OF ELECTRICITY IN K^

ENGINEERING AND SHIPBUILDING WORKS.

By A. D. Williamson, Member.

So much has been written on the subject of electric driving that it
is difiRcult to avoid repetition. The author will confine himself to facts
within his own experience, and not attempt to introduce published
results for which he is not responsible.
Vol. 32. 62

923 WILLIAMSON : APPLICATIONS OF ELECTRICITY [May 7th

The plant which will be described in this paper has been erected in
the works of Messrs. Vickers, Sons and Maxim, Limited, and amounts
in the aggregate to about 22,500 B.H.P. of generators and motors.

In 1896 Messrs. Vickers were commencing some considerable
extensions to their works, partly by building a number of new shops,
and partly by acquiring a ship3rard at Barrow-in-Furness and Sinaii
Gun works at Erith, resulting in an increase in the number of employes
from about 3,000 to nearly 20,000 during the four or five years following
1896. The great convenience of the motor -driving system soon became
apparent in connection with the rapid extensions. Generating plant
was ordered well in advance of actual requirements, and the speed at
which new shops were erected and started was limited only by the time
taken to deliver the structural steel work and machines. To quote one
instance of this, the South Gun Shop, now covering a ground space
660 feet by 200 feet, was built in a series of seven instalments, each
complete and working as soon as it was roofed over, movable corrugated
iron ends being erected to keep the weather out. The whole shop now
forms 6ne of the fipest machine shops in the world, and to all appear-
ances might have been built complete at one operation.

The first power-house was situated fairly centrally, and contained
four direct-driven sets of 160 k.w. shunt dynamos and 250 B.H.P.
compound non-condensing engines by Siemens and Belliss respectively.
The original intention was to use the current chiefly for cranes and
special armour-plate grinding machines which were difficult to drive
otherwise than by motors. At the same time, however, a new gun shop
was being built, and the opportunity was taken to apply motors, one to
each of the machines, most of which were large and required from 5 to
10 H. P. to drive them.

The success of the electric driving system under all the conditions
in which it was tried determined the directors to apply it to all the
extension work and, as opportunity occurred, to replace the less efficient
isolated steam plants.

Then, the first 1,000 H.P, power-house being loaded to its full
capacity, a larger power-house was built, on the south side of the works,
having a capacity of 1,325 k.w. As much ground was given for a site
as could be spared, and it was thought that the two power-houses
together would be quite large enough for the whole of the works when
all extensions were completed.

Later, however, it was found necessary again to increase the size of
the works, and this, added to the adoption of the Vickers high-speed
tool steel and the additional power taken by the machines in conse-
quence, rendered a third station necessary, containing one 350 k.w. set
and two 200 k.w. sets.

The total plant capacity at the Sheffield works is therefore 2,800 k.w.,
and the details of the three sets of plant *are shown in the following
table :—

I. North Power-house— 6^0 k.w.

Four engines, 250 BLH.P. each, compound non-condensing,
360 r.p.m.

1908.] IN ENGINEERING AND SHIPBUILDING WORKS. 997

Four dynamos, 220 volts, shunt, bi-polar Siemens.

Boilers. — Two Lancashire, two marine type, 160 lbs, fitted with

Ellis & Eaves' induced draught and Bennis stokers.
Feed heater, Berryman ; temperature of feed about 200' F.

2. South Power-house — 1,325 k.w.

Four Engines. — Three each 480 B.H.P. tandem compound con-
densing, Belliss enclosed type, three cranks, speed 300 r.p.m.

with 25 per cent, overload capacity.
One 530 B.H.P. triple expansion Belliss enclosed condensing

engine, speed 340 r.p.m. with 20 per cent, overload

capacity.
Four Dynamos. — Three each 325 k.w., shunt-wound, 220 volts,

6 poles, British Thomson Houston Co,
One 350 k.w., 8-pole shunt, 340 r.p.m., by Vickers, Sons, and

Maxim, Ltd.
Boilers. — Six Babcock and Wilcox, each evaporating 6,000 lbs. of

water per hour, with superheaters giving about 40* F.

superheat measured at the engine separators, 160 lbs.

pressure.
The stokers are of the chain grate type, driven by 5 H.P.

motor.
Economiser. — One Green's Economiser, 288 tubes, driven by a

li B.H.P. motor, giving an average feed temperature of

260'* F.
Condensers. — ^Three Wheeler Admiralty t3rpe, connected to a

common exhaust main so that any one or all may be used

as required.
Feed Pumps. — Weirs.
Oil Filters.— Harris.
Steam Pipes. — Steel, weldless. A complete duplicate system of

pipes, each main being connected to each engine and each

boiler, allowing repairs to be made on the idle main while

the plant is at work.
Pipe Covering. — Magnesia sectional.
Cooling water for condensers is pumped from the River Don by

a vertical turbine pump, driven by a 5 H.P. motor.

3. West Power-house-^jSo k,w.

Similar in general design to the others, but containing —
One 350 k.w. Vickers dynamo, 220 volts, 340 r.p.m.
One Belliss 530 B.H.P. triple expansion engine.
Two Bruce Peebles 200 k.w., 220-volt generators.
Two Sissons compound engines, by Markham and Co., Ltd.,

350 r.p.m.
Lancashire boilers, / 6" x 28'.
One Schmidt separately fired superheater, giving about 250° F.

superheat : Not yet started at time of writing.
Two watertube boilers are shortly to be put down, each to

evaporate 12,000 lbs. of water per hour.

928 WILLIAMSON: APPLICATIONS OF ELECTRICITY [May 7th,

4. Erith. In 1898 the works of the Maxim Nordenfeldt Co. were
purchased, and the old system of belt driving from one main engine
was replaced by electric power. A power-house was built containing
600 k.w.

Four Belliss and British Thomson Houston sets, each 150 k.w.
and 250 B.H.P., 220 volts, 360 r.p.m, with Wheeler con-
densers and multitubular boilers, 160 lbs. pressure.
As the works were at this time undergoing alterations and being
considerably extended, the convenience of motor driving was fully
appreciated.

Barrow. In 1897 the Naval Construction and Armaments Co. was
purchased, and the large works at Barrow-in-Furness were thoroughly
reorganised and extended, the number of men employed growing from
5,000 to 10,000 within three years from the time of acquiring the works.
The Barrow works presented a very fine opportunity for applying
electric power, and during the first year between 50 and 60 steam
engines were taken out with over a mile of steam pipes.

It may be mentioned here that the change from steam engines to
motors was made without in any way stopping the work. The change
was made quickly and without inconvenience — in fact it was half done
when the author was asked to state when the alterations were to
commence^ as much stoppage of work was expected.

5. The power-house on the Shipyard side contains the following—
750 k.w. ; —

Five 250 B.H.P. Mirrlees Watson compound 1 single-acting non-
condensing engines.

Five 150 k.w. British Thomson Houston shunt-wound, 6-pole,
2 20- volt generators.

Six 30 ft. X 8 ft. Lancashire boilers, 160 lbs.

One Berryman heater.

Twelve months saw this plant fully loaded, and it was decided to
put down a larger plant on the engine works side, as the engine
department had already become large users of the current for all their
extensions.

6. The Engine Works Power-house contains space for five sets, four
of which are installed —

Four Belliss triple-expansion engines each 700 B.H.P., 300 r.p.m.
Three 500 k.w. British Thomson Houston Co. 12-polc, 220-volt

shunt generators.
One 500 k.w. Vickers, Sons and Maxim 12-poIe, 220-volt shunt

generator.
One switchboard with 4 generator panels and 32 feeder panels.
Ten Lancashire boilers, 30 ft. by 8 ft., 180 lbs. working pressure

(8 in use at present).
Two Green's economisers, each 480 tubes, driven by 2i H.P.

motors.
Stokers — Bennis automatic, driven by a 10 H.P. motor (also

drives coal elevator).

1903.] IN ENGINEERING AND SHIPBUILDING WORKS. 929

Coal Conveyor. — Bennis, driven by a lo H.P. motor.

Ash Elevator and Motor. — Driven by a 5 H.P. motor.

Four Klein steam-driven sets of air and circulating pumps.

Two Klein cooling towers.

Two Klein jet condensers.
The two power-houses are connected in parallel, a system which is
adopted in the other works where there are two or more stations. This
plan enables one station to assist the other during temporary heavy
loads, and permits of either being shut down at times of light load.
Recording wattmeters are fitted in each dynamo circuit, and outputs
are recorded on log sheets for the purpose of checking costs.

There are three other works of the Company using electric power,
as follows ; —

7. iVor/A Kent Works, 186 H.P. 220 volts.

8. Wolsdey Tool and Motor Car Works, 350 H.P., 220 volts.

9. Electric and Ordnance Accessories Company, 560 H.P., 1 10 volts.
Making a total plant capacity of 1,180 B.H.P. or 786 k.w. for these
three works.

The author does not think it necessary to go further into details of
the generating plant, as it is all of a type familiar to the members of
the Institution and does not call for special description.

Reason for Adopting 220 Volts.

In 1895, when the choice was made, 220 volts represented advanced
practice, as incandescent lamps had only been for a short time on the
market for that pressure. No doubt a higher pressure would have
offered some advantages in the Sheffield and Barrow works on account
of the distances, but the difference between 220 and 250 is not reall>
very important. With 440 volts one must give up the idea of using
single glow-lamps unless the three-wire system is adopted.

It would be interesting, in the discussion, to hear the views of
engineers as to the suitability of three-wire distribution with 440 volts
across the outers, 'taking motors of 5 H.P. and upwards from the
440- volt mains, as well as all crane motors and others of intermittent
loading. Small motors with steady loads, as well as arc and glow
lamps, would be connected between the middle and outer wires. With
careful arrangement the system should do well in large works, and it
would have the advantage of giving variable speed-motors double the
range they would have on the ordinary two- wire system.

It may be thought curious that shunt generators are used in all
cases, as many power-stations have compound- wound generators. In
practice the author has found that with a fairly large generating plant
shunt generators are perfectly satisfactory, the pressure on the lamps
is quite steady. By the use of shunt machines the switchboard gear is
slightly simplified. If all the work had to be done again with a full
knowledge of the ultimate demand for power, it is probable that the

980 WILLIAMSON : APPLICATIONS OF ELECTRICITY [May 7th,

only differences would be in the direction of raising the voltage of
supply to 440, using three- wire distribution, and certainly making use
of the larger sizes of plant, each unit being 750 or 1,000 k.w. capacity.

The practice of installing small sets as well as large ones, which is
common and justifiable in lighting-stations, does not appear to possess
any advantages for heavy works driving, as the loads are fairly uniform
and of known duration. If the size of imit is chosen with due regard
to the ultimate plast capacity, allowing the standby set to bear a
reasonable proportion of the whole — say 20 per cent. — it is far better
to have all the units alike, with a full set of interchangeable spare
parts.

Cost of Production.

The systematic recording of all costs, properly subdivided, is of the
utmost importance. The weekly returns, when properly kept, are
sensitive indications of the state of the plant and also of the care shown
by the engine and boiler staff. Although the costs as shown in the
following tables are not as low as some which have been published
recentiy, they are of interest as representing the actual figures taken
from the books of the Works Cost Department. They are not made
out by the Electrical Department for show purposes, nor are they
the result of a week's test under exceptional conditions. They include
Sundays, holida3rs, and other '' unprofitable " times from a station
engineer's point of view.

Summary of Generating Costs (One Year).

Power House.

Present

Plant

Capacity

"icw."

640

Annual
Output

Fuel per
Ton.

Works

Costeper

Unit.

Total

Cost, per

Unit

(a) Sheffield, North

2,106,340

s. d.
9 H

*579d.

7i6d.

(6) Sheffield, South

J,325

2,610,620

7 H

•469d.

•675d.

750

Not long enou

ghinoper

ation for c

osts.

(d) Erith

600

1,430,500

20 0

I -id. (a

bout)

(e) Barrow Shipyard

750

644,500

17 0

r3d.(a

bout)

(/) „ Engine Works

2,000

3*504435

II 6

77ci.

•97d.

{g) Electric and Ordnance
Accessories Co. (Dow-
son Gas plant)

375

364,000

19 10

•55d.

t Fad
1 and

Total Output (including smaller works) = 1 1,000,000 units per annum.

Notes,

(a) Fully loaded.

(b) Not fully loaded ; the plant capacity during the period of test was only
975 k.w. ; the fourth set has only been put down recently. This station can
easily turn out 4,000,000 units annually.

1908.] IN ENGINEERING AND SHIPBUILDING WORKS.

931

{d) Inclucies pumping all works' water with steam from these boilers.

{€) Comparatively lightly loaded, and includes steam supplied to a
hydraulic plant.

(/) The building, pipes, condensers, and cooling towers are complete, and
the plant capacity was only 1,500 k.w. during the year of test, while the
power-house will accommodate 2,500 k.w.

Charging the proper proportion of the final capital cost against the present
plant for the year, the interest and depreciation amount to *2d., making total
cost =3 *97d. per unit.

ig) The works having been recently acquired, further information is not
available.

Capital Outlay on Plant and Buildings (Various Works).

£ s.

Sheffield, North ...

20 10

0 per killowatt

Sheffield, South ...

25 i6

0 „ .,

Erith

22 10

0 „

Barrow Shipyard ...

24 3

0 „

Barrow Engine Works

26 10

0 „

Electric and Ordnance

Company

26 5

0 „

The most interesting figures are those relating to the Sheffield
works, and an analysis of the cost is given below : —

Power House.

Item.

North.

South.

Coal

. -313

•255

Water

.. '046

•016

Wages and Supervision

. -102

•lOI

Stores

. 017

016

Repairs

. -loi

•o8i

Works cost ..

. -579^.

•469d,

Taxes

...

. 027

•026

Share of Works Railway,

Carting

Coal and Ashes, Boiler Insurance,

. -004

•004

Employer's Compensation,

etc.

Interest and Depreciation ...

...

.. -106

•177

Total Cost per Unit

...

. 7i6d.

•675d,

The difference in the costs is due partly to the variation in the price
of coal according to the locality, and partly to the nature of the load
factor.

The Sheffield works possess the best load, lasting through the
entire day and night (day load, 5,150 amperes; night load, 4,500
amperes). This refers chiefly to such work as steel melting, armour-
plate and gun work, which must go on continuously. The other works
make less use of night work, although a good deal is done at Barrow
and Erith at times.

The amount of standby plant is determined by the number of
working hours. In the case of a railway wagon shop for which the
author acted as consulting engineer; no spare plant was put down, nine

932 WILLIAMSON : APPLICATIONS OF ELECTRICITY [May 7tb.

hours being the usual working day. These hours of working permitted
all repairs and repacking of the engine to be done during the stopping-
time, and no need of spare plant has ever been felt. The usual
practice is to allow 25 per cent, of standby plant when all the sets are
installed.

It is interesting to compare the results of the north and south
power-houses at the Sheffield works. Both work on exactly similar
loads, in fact they are connected to a common network ; one is con-
densing and has economisers in the flue, the other is non-condensinj^
and has exhaust steam feed-heaters. The non-condensing station has
sets only half the size of the condensing station, and there is a difiFerencc
in the cost per unit of about -^d. in favour of the condensing station
accounted for in coal and water alone.

Finally, before leaving the subject of generating plant, the author
would like to state that his experience of high-speed vertical engines
running under the severe conditions of continuous heavy loads has
been perfectly satisfactory. The cylinder liners of some of the engines
have been carefully gauged after five years' work, and show practically
no wear.

Distribution Mains and Wiring.

In almost every case the main cables are overhead, on insulators
carried partly by posts and partly by the buildings. A light insulation
is used to avoid short-circuits where wires come accidentally into
contact, blown by the wind, as well as for the protection of telephone
and other bare wires. A few underground cables have been used, but
the ground in the steel works is timnelled by flues carrying hot
furnace gas, and it is i not, therefore, often found possible to use under-
ground mains. A lead-covered concentric cable, 220 yards in length,
carries current to a pumping station at the riverside through a tunnel,
which is often filled with water in rainy times. The motors in the
pumping station are of 60 B.H.P. capacity.

Motors.

It must be owned that most of the success of electric driving
has been due to the great improvements which have recently been
made in manufacturing motors. Certainly there are still numbers of
the old motors in use which were put down six years or more ago,
but if the old smooth-core armatures had not given way to the more
robust tramway type of armature, many of the applications of elec^ic
driving could not have been made. The motor and starter of six or
seven years ago were things to be handled with care, and hardly to be
trusted to an ordinary workman to start. Now, Messrs. Vickers have
over 1,300 motors in use, all of which are started and controlled by the
workmen attached to the machines or cranes, and, in spite of the very
rough usage still common in the shops, it is wonderful how well the
modern machines take care of themselves.

At the outset a strong effort was made to cut down the number of
sizes of motors, and also to secure interchangeability of the armatures

1903.] IN ENGINEERING AND SHIPBUILDING WORKS. 933

and other parts likely to require replacement. Once decided upon, a
type of motor was kept as a standard until a sufficient reason caused it
to be superseded. For instance, perhaps twenty or thirty motors of
lo H.P. were ordered, with a spare armature to fit any of them. When
these motors were all used, it was considered that one spare armature
might fairly be allotted to those twenty or thirty motors, and if a better
type of motor of that size were available there was no objection to
sulopting it, and having a spare armature for the new type.

The following list gives particulars of the standard motors and their
speeds :—

' RHP.

TyiH-.

Speed.

Semi-enclosed

1,200

»i >f

800

II II

600

Enclosed

600

Semi-enclosed

Variable — 300 to 000

If II

600

Enclosed

600

Semi-enclosed

Variable— 300 to 900

}t 11

600

f> II

600

» >t

600

i 25

t> II

Variable — ^300 to 900

*t II

500

tf II

500

f* II

500

II II

400

Of course there are a certain number of other types, on cranes and
small portable tools, but the same principle of interchangeability and
few t)rpes has been a ruling factor throughout.

These speeds are lower than many makers call their standards, but
when one considers that in nearly every application the speed has to be
reduced to quite a small proportion of the original speed at the point
of utilisation, it will be seen that a low initial speed is a great advan-
tage, often counterbalancing the rather higher cost of the motor. No
hard and fast rule can be made determining the size of machine which
should be driven by a separate motor. At iirst it was decided to make
5 B.H.P. the smallest motor for a single machine, but many cases arose
where it was found advantageous to put a motor of 2 or 3 H.P. on a
machine which only worked intermittently.

The use of single motors has proved of great convenience in
placing machines, rendering them independent of the line shaft; it
also allows a free space for the travelling cranes to work in by dispensing
with the network of overhead belting. As regards actual efficiency
during working time there is little to choose between line shaft driving
and separate motors, although the difference is in favour of the separate
motor system unless the smallest motors are used. Considering a line

884 WILLIAMSON : APPLICATIONS OK ELECTRICITY [May 7th.

of ten lathes, each of i8-inch centres, driven in three alternative
ways, viz. : —

(i) By one 40 B.H.P. motor and line shaft no ft. long.

(2) By ten 5 B.H.P. motors, constant speed, with step cones for

varying speed. Belt drives.

(3) By ten 5 B.H.P. motors, variable speed, mounted on the lathe

headstocks, and no belts.

The capital outlay and losses zifull load are set out in the following
table :—

COAtof

Driving
Arrangements.

Loss in

Shafts and

Belts.

Loss in
Motors.

Total Loss.

(i) 40 H.P. motor. 1
Machines in 2 V
rows of 5 per row j

(2) Ten 5 H.P. motors)
(constant speed) 3

(3) Ten 5 H.P. motors )
(300 to 900 speed)

4 E.H.P.
2 E.H.P.

4 E.H.P.

75 E.H.P.
75 E.H.P.

8 B.H.P.

9 B.H.P.
75 B.H.P.

In the case of the 40 H.P. motor there is a fixed loss of about
4 H.P. in shaft and belts, when the shaft is running and no lathes
working. With no lathes working in the cases 2 and 3 there is
no consumption of energy. With five of the ten lathes working the
comparison is as follows : —

Loss in Shaft
and Belts.

LoKtin
Motors.

Total Loss.
B.H.P.

40 H.P. motor

Five & H.P. motors, con- )
stant speed 3

375

475

Five 5 H.P. motors, vari-)
able speed ... * J

—

375

Working conditions would be fairly represented by assuming eight out
of ten machines to be in use, the remaining two having tools or work
changed or set.

The choice really lies between the 40 H.P. motor and one of the two
separate motor systems, and of these two the variable-speed system is
certain to l)e preferred by any one :wbo has had experience of its

1903.] IN ENGINEERING AND SHIPBUILDING WORKS. 936

convenience. Comparing S3rstems i and 3 for working cost under
average conditions, the results are approximately as follows : —

Eight lathes working out of ten —

Total loss— System i = Ji B.H.P.

ty >» 3 ^ " f*

One B.H.P. is practically one unit at the switchboard, there is thus
a saving of i J units per hour, or ijd. per hour at 75d. per unit This
amounts to 5s. per week of fifty-four hours, and £12 per annum. From
this saving must be deducted the interest at 4 per cent, on the
di£Ference in the capital outlay, which is equal to ;£ii per annum,
leaving the apparent balance of only £2 per annum in favour of the
variable-speed motors.

This saving is the minimum, as the working conditions do not
always prevail, and for every hour of overtime work with only one or
two lathes working there is a large balance in favour of the small
motors. As the load diminishes below half load on the large motor
its efficiency falls away rapidly, while the small motors are always
working at a high efficiency when working at all. The output of work
is largely increased by not requiring belts to be shifted in the
latter case.

The above case is not particularly favourable to variable-speed
motors ; the price per unit is usually above 75d. in works only run-
ning fifty-four hours per week. Working continuously 5i days per
week, the nett saving would be i^. x 132 = 12s. 4d. per week or £22
per annum, less ;^ii interest = ;^2i per annum, plus the large saving
due to increased output and reduced power costs for overtime work.

No doubt the first cost prevents many owners of works from adopt-
ing separate motor driving, but where money can be raised at a cheap
rate of interest there is little doubt that that system is the more
economical one where the machines are of sufficient size to justify
the use of separate motors. Unfortunately it is a conmion habit, when
electric driving has been decided upon, for the works manager or
engineer, with no special knowledge of the subject, to take the settle-
ment of all the details on himself, with the result that many of you must
have seen. Electric driving will not necessarily cheapen production
in all cases, and unless it is undertaken with some knowledge and a
good deal of thought, it may affect the cost of producing work
adversely.

The author has had to advise in the case of some works where the
conditions appeared to be most favourable to electric driving at first
sight. The engine was about 40 years old, the shafts, belts, and
general arrangements were as badly planned as could be, and yet, on
carefully estimating the cost of conversion and probable saving, there
was 'SO small a margin that he advised the retention of the existing
plant in the interests of economy. The percentage saving would have
been considerable, but the coal bill and other costs were so low that
the financial results would have been disappointing. For the same
reason, it is only where the conditions are very favourable that electric

936 WILLIAMSON : APPLICATIONS OF ELECTRICITY [May 7th,

driving can replace the older system economically in parts of the
country where coal is cheap.

The particular case referred to above was that of a small compact
factory, in three stories, covering but a small ground space. The steam
pipe was very short, and the losses were chiefly in the shafts and belts.
As the machines were many and small, it would have been impossible
to dispense with the shafts, and only the main belts from floor to floor
would have been saved by motor driving. Had the works consisted of
isolated shops instead of floors, the case would have been entirely
favourable for electric driving.

The number and horse-power of the motors in the various works of
the Vickers Company are stated in the following table, which divides
them into three classes, viz. : —

(i) Motors working continuously.

(2) Motors on cranes and hauling gear.

(3) Motors performing auxiliary operations, such as travelling lathe

saddles and other occasional work of very short duration.

The average current absorbed by the motors in each case is also stated,
and it is a rough indication of the size of generating plant required for
dealing with such a load. Of course this figure naturally varies accord-
ing to the proportion of crane motors to those of steady loading, but it
may be of use to engineers when considering new cases of a similar
nature.

Total number of motors (all the works) = 1,311.

Total B.H.P. of motors „ „ = 12,40a

Table Showing Motors Installed and Average Loads.

Works.

No.

Sheffield ] 299

Barrow...
Erith ...
Wolselev

Shafting and
Machine
Motors.

80
14

North Kent| 11

Elec & Ord
(no v.).

B.H.P.
2464

3388
862

Crane
Motors.

No. I B.H.P
170 I 2683

33' 216

1601 —

122: — — ' — , —

300 —

Intermittent

Load

Motors.

B.H.P.

No. B.H.P.
174! 657

Total.

1
~ 1 ""

4930

— 1 —

1078

— ' —

160

-1 -

122

_' _

Gearing.

The question of type of gearing is of great interest ; few machines
lend themselves to direct driving by motors of reasonable speed

1903.] IN ENGINEERING AND SHIPBUILDING WORKS. 937

without the interposition of a certain amount of gearing. Fans,
saws, and some woodworking machines arc practically the only cases
where high speeds are required. The choice of gearing is not very
wide. The types may be divided into the following classes : —

(i) Worm Gear.

(2) Spur Gear with metal wheels.

(3) Spur Gear with metal and raw-hide.

(4) Spur Gear with mortice wheels.

(5) Friction Gear.

(6) Chain Gear.

(7) BelHng.

The author has tried all the above, and finds that only spur gear, chain
gear and belting are of real use, except in special cases.

Worm Gearing, to be efficient, must be fitted with ball thrusts, run in
oil, and must be very well made. It is expensive, but where great
speed reduction is required it is useful, especially in such cases as hoists,
where the work is occasional and the efficiency of minor importance.

Friction Gear is inefficient and cannot be applied for large powers.

The three classes of Spur Gear are all good ; the speed and per-
missible amount of noise determines which class should be adopted. The
author places a limit of about 1,000 feet per minute for metal spur gears,
beyond which the noise becomes unpleasant in ordinary machine shops.
At this speed, cut gears with well-formed teeth are necessary. Raw-
hide and metal can easily be used up to 2,000 feet per minute.

Belting is of course applicable to nearly all cases, the slipping being
a positive advantage where heavy shocks and reversals of machines
take place.

Chain GearinghsiS the advantage of silence and positive driving; it is
most suitable for short drives. Renold chains from 5 to 80 H.P. are
used in the Sheffield and Barrow works, with excellent results. Chain
drives are only fit for shops which are clean and free from dust and
grit, unless special steps are taken to case them in well. A common
method of line shaft driving is to fix the motor to a column or wall
bracket and drive the shaft by a chain, the centres of the shaft and
motor being about three or four feet apart. This economises floor
space, and a speed reduction of 6 to i is easily obtained, as the chain
wheel may be considerably smaller than a belt pulley transmitting the
same power.

Variable-Speed Motors.

The problem of varying the speed of motors without loss of effi-
ciency has received a good deal of attention during the last few years,
and there is now no difficulty in building motors with a range of
three to one, or even more, by varying the field excitation. The
limiting factor is the highest speed to which it is permissible to go
from mechanical considerations, and the range and lowest speed
depend on the price to which one is prepared to go. A three to one
range appears to be about the most economical one for motors of fair

938 WILLIAMSON : APPLICATIONS OF ELECTRICITY [May 7lh,

size, say from 250 to 750 revolutions, or 300 to 900 revolutions for motors
from 5 to 30 H.P. Any reduction of speed below about 300 causes the
weight and price to rise rapidly.

The author's firm is now building motors which work sparklessly
with fixed brushes with a speed variation of three to one, and it is only
on account of the difficulty of arranging satisfactory mechanical drives
that higher maximum speeds are not used.

An application of variable-speed motors which the author believes
to be novel has been recently used in the electrical manufacturing
shop of Messrs. Vickers. A portable vertical planer or slotting machine
is driven by a 5 B. H.P. motor with a range of speed from 300 to 900,
the motor being attached direct to the machine. On the cutting stroke
the motor runs at its slowest speed, and at the end of the stroke, the
length of which is easily adjusted to suit the work, the motor reverses
automatically. As soon as the reversal has occurred a resistance is
automatically inserted in the field winding, quickly raising the speed
to 900 for the return stroke. At the end of the quick return stroke,
immediately before reversal, the field resistance is short-circuited,
providing a strong field for reversing in, and the motor reverses and
makes its slow cutting stroke, the cycle repeating itself. The insertion
and removal of the field resistance necessitates a special form of switch
which is provisionally protected and cannot at present be descrit)ed in
detail. The arrangement has been in use for some time successfully,
and it is anticipated that it will be of great use in driving many types
of reciprocating machines. In actual practice it is found that this
method of driving is very economical and possesses advantages over
the usual belt reversing drive, as the excess current at reversing can be
reduced to a negligible quantity.

There are about no variable-speed motors in the Sheffield works
driving lathes and gun-boring machines, and they do their work most
satisfactorily. They were all built by the electrical department of the
Company.

There is a great saving of time in such operations as parting off
heavy shafts, the turner being able to follow the work as the diameter
diminishes and keep his cutting speed at its maximum without having
to shift his belt from step to step.

While the motors for line shaft and machine driving are almost
invariably shunt- wound, there are cases where the conditions call for
heavy starting currents, and compound motors or pure series motors are
used. Such machines as punching and shearing machines, angle and
beam cutters, and other shipyard and boiler-shop tools, have heavy
flywheels, requiring large currents to accelerate them. The work is
done by a temporary fall in speed of the flywheel, and the light-load
current does not fall below about half the full-load current. Here
series machines are excellent, a constant speed is not required, and
there is always sufficient load to keep the speed from reaching a
troublesome limit.

Reversing motors do not seem to be in use to the extent that their
merits entitle them to, and it is a very conunon thing to see plate-
bending rolls and straighteners driven by a motor belted to a counter-

1903.] IN ENGINEERING AND SHIPBUILDING WORKS. 989

shaft, which drives the machine by open and crossed belts. The space
occupied is considerable, and the belts usually slip a good deal. There
is no difficulty whatever in arranging good compact drives with
reversing motors driving through spur gearing. In the Barrow Ship-
yard there are several rolls driven thus, by 45 and 30 H.P. motors.
Liquid controllers are used for these, and in the Sheffield works some
rolls for bending 3-inch gun shields are driven by 22 H.P. tramway
motors with standard tramway controllers.

Some of the most interesting examples of electrically driven
machines are described in the following table of tests, and although
many of them may be very similar to results published in other papers,
the author hopes that, taken in bulk, they may be of use to engineers as
a table of reference. The machines are divided into 11 classes as
follows : —

1. Lathes and Boring Machines.

2. Planing Machines.

3. Slotting Machines.

4. Shipyard Plate Machines (Punchers, Shears, Countersinks,

Angle cutters, Rolls).

5. Drilling Machines.

6. Pumps.

7. Cranes.

8. Saws for Metal.

9. Wood-working Machines.

10. Special Machines.

1 1. Fans and Blowers.

The method of setting out the tests may seem cumbersome, but unless
the conditions are clearly stated and the method of driving described
in some detail, the results are of little use.

Class I. — Lathes and Boring Machines.

Machine. 36 in. Centre Lathe. 90 /f. long.

Drive. By a short belt from rocking countershaft Motor drives

countershaft by steel spur gearing.
Motor. 10 B.H.P. 600 r.p.m. Shunt.

Work, 9'2 in. gun tube. Weight about 5 tons, diameter
20 in. Hard steel, cutting speed 5 ft. per minute.
4 cuts tV in. X ^ in. traverse = 6-8 B.H.P.
4 cuts Tf in. X J in. traverse = 7*5 B.H.P,

Another test on same lathe: —

Work. Mild steel shaft, 11 in. diameter, 16 ft. long.

Cuts I in. X i in. traverse. Cutting speed 10 ft. per

minute.
With no cut Lathe takes 3-1 B.H.P.
With I cut „ „ 4*6 „
With 2 cuts „ „ 5-5 „
With 3 cuts „ „ 70 „
With 4 cuts „ „ 9*4 „
Rising after half an hour to 10*5 B.H.P.

940 WILLIAMSON : APPLICATIONS OF ELECTRICITY [May 7th,

A similar 36 in. Lathe driven by 10 B.H.P. variable-speed motor,
250-500 r.p.m. through steel spur gearing ; —

Work, 23-ton gun tube, forging hard steel.
Running light = '6 B.H.P.
4 cuts J in. X J in. traverse. 107 B.H.P.
Cutting speed 5 ft. per minute.
Machine. 40 in. Centre Lathe,
Drive. Belt from motor to countershaft.
Motor. 10 B.H.P. shunt. 600 r.p.m.
Work. Mild steel shaft 36 ft. long, 18 in. diameter, 24 tons.

4 parting cuts each i J in. wide x '05 traverse. 9 B.H.P.

taken.
Running without cuts, 3-5 B.H.P.

Tests of Power taken by Lathes using Vickers' High-Speed
Tool Steel.

Lathe.

Material.

Cutting
Speed.

No. of
Tools.

Lbs. of

Metal

per hour.

.«7

Cut.

Tra-
verse.

!B.HP.

Lbs. of

Metal per

B.H.P.

hour

36" Centres

Gun Steel

12' per min.

38"

•166"

„

21' .,

280

•3H"

•166"

»5'4

182

„

32' .,

360

•26"

•166"

15-4 1

234

•t

„

12' „

460

28"

•166"

19-8 1

232

„

Gun (very
hard)

8' „

■50"

•143"

15-0 1

7-33

„

Gun steel
ingot

51' .. ,

502

99"

•05"

255

197

1 Gun steel
1 ingot

4«' .. '

570

•58"

•lO"

330

.7-3 1

Marine shaft
(32 tons ten-
sile) '

4fio

•50"

•10"

220

21-8

1
1

40" Centres

Marine shaft

13-5' M

r/w

•3"

•25"

30" ., 1 Gun steel i

18'

705

•45"

•188"

30 1

265 1

. -

- -

- _'

^ "

X(?/f:. — Allowing a tool to cut at such a rate that it requires grinding after
two hours' work, the weight removed per hour is about 220 lbs. per tool, and
the B.H.P. is about n per tool. A lathe with four tool posts can therefore
absorb over 40 H.P., but as the four tools are not always cutting equally
heavily in roughing, most of the lathes used for roughing in the Sheffield
works have motors of 30 B.H.P., with overload capacity up to 40 B.H.P.

Twenty lathes of from 30-inch to 40-inch centres are having 30 H.P.
motors fitted in place of the former 10 H.P. motors.

Boring Machines,
Machine. 24 in. Centre Gun Boring Lathe,
Drive, Motor to countershaft spur gear, belt to lathe.
Motor, 5 B.H.P. shunt, 600 r.p.m.

Work. 6 in. gun tube, boring 8 in. hole out of solid, 3 inches
per hour. (Ordinary tool steel.)
54 B.H.P. 57 lbs. steel per B.H.P. hour.

1903.] IN ENGINEERING AND SHIPBUILDING WORKS.

941

Machine, Ingot and Tube Boring Machine,
Drive, Through steel spur gearing.
Motor. lo B.H.P. shunt, 600 r.p.m.

Work. Boring 9 in. hole from the solid in 27-ton gun forging
(which is rotated).
Traverse 2J in. per hour. (Ordinary tool steel.)
B.H.P. = 55. 84 lbs. steel per B.H.P. hour.

Another Test: —

Boring 12 in. hole from solid in 15-ton ingot.
Traverse 2^ in. per hour.
B.H.P. = 72. 11-25 lbs. steel per B.H.P. hour.

Fig.

Machine, Double-Barrel Bonng Machine for 6 in. Guns.
Drive, Spur gear and worm gear.

Motor, 10 H. P. Vickers variable speed, shunt, 350-500 r.p.m.
Work. Boring a gun tube from both ends.

Diameter of hole 7tV in. one end, 6J in. the other end.
Traverse 2 J in. per hour each end. (Ordinary tool steel.)
B.H.P. =804. 754 lbs. steel per B.H.P. hour.

Machine, 6 in. Gun Boring Machine,

Drive, Spur and worm gearing.

Motor. 25 B.H.P., variable speed 300 to 900 r.p.m.
Vol. 82. 68

942 WILLIAMSON : APPLICATIONS OF ELECTRICITY [May 7th,

Work, Boring 5 ^ in. diameter hole out of solid gun steel at
the rate of 42 in. per hour (21 in. each end) with
Vickers' high-speed steel. Power taken ^ 25*5 B.H.P.

Machine, 12 ft, X 12 ft, X 25 /if. 6 in. Planer, (See Fig. i.)

Gear. Spur gear and belt reversing.

Motor, 40 B.H.P., shunt, 720 r.p.m.

Work, Parting a 12 in. nickel steel armour plate, 23 tons.

2 tools, each i^ in. wide, cutting speed 12*5 ft per

minute.
Quick return stroke 30 feet per minute.
Cut and quick return take 17 B.H.P. Reversing takes
up to 70 B.H.P.

Class II. — Planing Machines.

Machine, Heavy Armour-plate Planer, 10 ft, 6 in, x 10 //. 6 in. x

2$ ft, stroke.
Gear, Belt drive, open and crossed belts (8 in. wide, double).

Motor. 15 B.H.P., 400 r.p.m., shunt- wound.
Work, (i) Running without cuts, 4-ton plate on table.
Cutting stroke, 4 B.H.P.
Reverse slow to fast stroke, 20 B.H.P.
Quick return stroke, 9 B.H.P.
Reverse fast to slow stroke, 12*5 B.H.P.
Extra for each cut i J in. wide parting tool on nickel
steel plate = 2 B.H.P.
(2) 12 in. nickel steel plate, 30 tons.
Cutting stroke (no cut on), 7 B.H.P.
Reverse to quick stroke, 24 B.H.P.
Quick return, 15 B.H.P.
Reverse to slow stroke, 15 B.H.P.
The cutting speed was 5 ft. per minute. The cuts were

on the hard Harveyised surface.
Extra for each ij tool = 2 B.H.P.

Machine, Side-planing Machine for A rmour Plates,

Gear. Open and crossed double 4 in. belts.

Motor, 5 B.H.P., shunt, 600 r.p.m.

Work. 6 in. nickel armour-plate, cutting in both directions.

Running machine without cut, 1*4 B.H.P.

Cuts } in. wide parting tool.

(i) Cutting the hard face, 5 ft per minute, 4 B.H.P.

(2) Cutting below the hard face, 9 ft. per min., 5*5 B.H.P.

Machine, 4//. 6 in. x 4//. 6 tn, x 12 ft. stroke Planing Machine.

Drive. By belt from motor.

Motor. 10 B.H.P., shunt, 600 r.p.m.

Work. Running belt on loose pulley, 3 B.H.P.

1903.] IN ENGINEERING AND SHIPBUILDING WORKS.

948

Cutting stroke (no cut on) 19*5 ft. per minute, 3 B.H.P.

Reverse, maximum, 25 B.H.P.*

With 30 cwt. steel forging, two tools cutting 19*5 ft.

per min., 5 B.H.P.
Reverse to quick return, 25 B.H.P.*
Quick return, 69 ft. per minute, 7 B.H.P.

Machine, Planer, 5//. 6 in. x 5//. 6 in, x 12 /if. stroke.

Drive, Motor on planer drives countershaft direct at 300 to

400 r.p.m. Open and crossed belts to pulleys.
Motor. 10 B.H.P., shunt, speed variable from 300 to 400 r.p.m.
Work. Planing cast-iron motor frames.

Cut J in. X "^B in., 16 ft. per minute (2 tools).

Quick return, 43 ft. per minute, 5 B.H.P.

Reversing takes 15 B.H.P.

Cutting takes 4*5 B.H.P

Class III. — Slotting Machines.

Machine. 30 in. Stroke Slotter,
Drive. Belt.

Motor. 5 B.H.P., shunt, 600 r.p.m.
Work. Slotting gun breech ring, about 24 in. stroke,
(i) Cut i in. X A in- traverse, 2 B.H.P.

(2) Roughing cut i in. X A in. traverse, 4*5 B.H.P.
Quick return stroke, i B.H.P.

(3) The heaviest observed current on any work which the

machine will do was equal to 6 B.H.P.

Machine. ' 36 in. Stroke Slotter,

Drive, Belt.

Motor. 10 B.H.P., shunt, 600 r.p.m.

Work. Cutting mild steel, i J in. x iV in, traverse, 28 in. stroke.

Cutting, 7 B.H.P.

Reverse to quick return, 9 B.H.P.

Quick return, 5 B.H.P.

Reverse to cut, 7 B.H.P.

9 lbs. of steel per B.H.P. hour.

Class IV.— Shipyard Plate Machines.

Machine. Large Plate Rolls, 30 in. wide.
Drive, Main drive by spur gear into two bottom rolls.
Motor, 45 B.H.P., series reversing, 450 r.p.m., enclosed.
Work, Reversing rolls, about 50 B.H.P. (momentary).
Running rolls light, 15 B.H.P.

• After fitting a CI. disc 33 in. x 2 J in. on the motor as a flywheel, the
reversing H.P. was reduced to 16. As the motor had a high sparking limit, it
was kept on the work ; the heavy load was not of sufficient duration to affect
the temperature.

944 WILLIAMSON : APPLICATIONS OF ELECTRICITY [May 7th,

Bending i6 ft. x i} in. cold plate —
Reversing rolls up to 80 B.H.P. (momentary).
Running, 25 to 30 B.H.P.
A magnetic brake was fitted to stop the motor quickly.
It lifted at 45 amperes.

Lifting Gear for above Rolls. Top Roll, 30 in, diameter.

Gear, Bevel and worm gear, reduction 100 to i.

Motor, Two 10 B.H.P. series, 600 r.p.m., one each end of roll.
Work, Raising one end, 10 B.H.P.
Raising both ends, 18 B.H.P.
Lowering one end, 8 B.H.P.
Lowering both ends, 15 B.H.P.

Pressing the roll on to a 9 ft. x i in. steel plate,
22 B.H.P.
When motors were brought up all standing, the maximum

current rose to 160 amperes. No damage done.

Magnetic brakes fitted to each motor to check the rolls with

accuracy when lifting and lowering.

Machine, 6 ft. 3 ///., Vertical Rolls.
Drive. Spur gearing.

Motor. 22 B.H.P. tramway motor, 575 r.p.m.
Work, Bending 3 in. nickel steel gun shield to about 24 in.
radius, at dull red heat.
Average load, 25 B.H.P.
Maximum observed, 35 B.H.P.

(As the work is intermittent, the above motor is found
to be quite strong enough.)
Auxiliary Motor. 5 B.H.P. series, 600 r.p.m., for feeding the rolls
in bending. Fully loaded.

Machine, 10 in. Boiler Shop Rolls (converted from engine drive).
Drive. Belt to countershaft carrying old engine pulley and

open and crossed belts to machine. Speed of rolls

10 r.p.m.
Motor. 10 B.H.P., shunt, 600 r.p.m.
Work. Running open and crossed belts on loose pulleys,

35 B.H.P.
Rolling 1% in. cold plate into 19 in. diameter tube

8 ft. 2 in. long, 11 B.H.P.
Reversing. No noticeable increase.

Machine. Shipyard Rolls — 20//. 6 in. Rolls,

Drive, Open and crossed belts to shaft carrying old engine

pinion.
Motor, 30 B.H.P., series, 600 r.p.m.
Work, Rolling § in. plate, 30 in. wide, 9 B.H.P.

Rolling i in. plate, 15 in. wide, 12 B.H.P.

Reversing, 32 B.H.P.

1905] IN ENGINEERING AND SHIPBUILDING WORKS.

945

Machine. Plate Straightener (" Mangle ").
Drive. By open and crossed belts.
Motor. lo B.H.P., shunt, 600 r.p.m.
Work. Running rolls light, 3 B.H.P.

Rolling J in. plate, cold, 42 in. wide, 4 B.H.P.

Rolling ^ in. plate, cold, 48 in. wide, 8 B.H.P.

Reversing, about 10 B.H.P.

Machine. Small Shearing Machine (used far shearing Rivets).
Drive. By fibre pinion and cut steel wheel.
Motor. 5 B.H.P., shunt, 600 r.p.m.
Work. Running light, 15 B.H.P.

Shearing one i in. rivet at a time, 3 B.H.P.

Shearing three f in. rivets at a time, ^i B.H.P.

Machine. Shipyard Punch and Shears.

Drive. Belt to flywheel from motor in pit. Converted from

steam engine drive.
Motor. 5 B.H.P., series, 600 r.p.m.

Work. Punching ij in. holes in } in. ship's plate, 6 B.H.P.
Shearing i in. plate, 9 B.H.P.

Machine. Heavy Punch and Shears {Three-headed Machine).
Drive. Belt to flywheel from motor on entablature carried by

derrick standards. Converted from engine drive.
Motor. 20 B.H.P., series, 600 r.p.m.
Work. 26^ strokes per minute.

Running light, engine still connected, 9 B.H.P.
Running light, engine disconnected, 3*5 B.H.P.
Shearing i in. plate, 17 B.H.P., rising to 24 B.H.P. on a

long plate.
Punching i in. holes in J in. plate, 7 B.H.P.
As not more than two heads are in use at once, the motor
is found to be quite large enough.

Machine. Horizontal Beam Punch and Shears.

Drive. Belt to flywheel from motor on entablature.

Motor. 10 B.H.P., shunt, 600 r.p.m.

Work. Running light, 30 strokes per minute, 2*5 B.H.P.

Starting current, 13 B.H.P.

Shearing angle bar, 5 in. x 3 in. x i in., 5 B.H.P.

Shearing bulb bar, 9 in. x 3^ in. X i in., 9 B.H.P.

Shearing angle, 4 in. x 4 in. x | in., 9 B.H.P.

Shearing angle, 6 in. X 6 in. x i in., 13 B.H.P.

Shearing bar, 6 in. x i in., 5 B.H.P.

Shearing angle, 3 in. x 2i in. x } in., 3 B.H.P.

Machine. Squeezer for Straightening Bars and Rails.

Drive. Belt from motor on old engine standard.

Motor. 5 B.H.P., series, 600 r.p.m.

Work. Running light, 2 B.H.P.

916 WILLIAMSON: APPLICATIONS OF ELECTRICITY [May 7th,

Straightening a rail, 2^ B.H.P.
Starting, about lo B.H.P.
The flywheel is very heavy, weighing over i ton.

Machine. Three Plate Countersinks.

Drive, Belts from a 40 ft length of 3 in. shaft. Motor drives

shaft by belt.
Motor. 10 B.H.P., shunt, 600 r.p.m.
Work. Running three belts on loose pulleys, 2 B H.P.
Running three machines Hght, 3^^ B.H.P.
Three if in. holes countersunk at once in f in. plates.
Speed of countersinks 130 r.p.m., 11 B.H.P.

Machine. Two Countersinks and one Edge Planer.
Drive. Belts from 70 ft. of 3 in. shaft, 160 r.p.m.
Motor. 10 B.H.P., shunt, 600 r.p.m.
Work. All machines on loose pulleys, 3 B.H.P.

Two countersinks working, 8 B.H.P.

Planer alone, J- in. plate, iV ii^* cut, 16 ft per minute^
10 B.H.P.

Average load, usual conditions, about 14 B.H.P.

Machine. Scarphing Machine {two Shaper Heads).

Drive. Belt drive.

Motor. 5 B.H.P., shunt, 600 r.p.m.

Work. } in. ship's plate, both heads working.

Cut, taper from } in. to i in. deep x tV in* traverse =
6 B.H.P.

Machine. Large Edge Planer (25 //. stroke).
Drive. Belts, open and crossed.
Motor. 20 B.H.P., shunt, 600 r.p.m.

Work. Planing i in. plate, ^ in. cut, 14 ft. per minute =
18 B.H.P. Reversing did not exceed this.

Machine. Small Edge Planer {12 ft. stroke).
Drive. Belts, open and crossed.
Motor. 10 B.H.P., shunt, 600 r.p.m.
Work. Planing a ship's plate on the surface.

Cut 2^ in. wide X tV in. deep, 14 ft. per min. = 15 B.H.P
This is unusually heavy work for this machine ; it seldom
takes more than 10 B.H.P.

Class V. — Drilling Machines.

Machine. Portable Drill up to 2 in. Diameter.
Drive. Spur gear reduction and Stowe flexible shaft
Motor. 2 B.H.P. Variable speed, 750 to 1,000 r.p.m.
Work. 2 in. hole in mild steel.

Rate of feed, 0*15" per minute.

Speed of drill, 30 r.p.m. = 15 B.H.P.

1903.] IN ENGINEERING AND SHIPBUILDING WORKS.

947

Class VI.— Pumps.

Machine, Centrifugal Pump, i8 in. Outlet,
Drive, Renold chain.
Motor, 70 B.H.P., 600 r.p.m., shunt

Work, Lift 29 ft. (maximum) 5,500 gallons per minute. Speed,
275 r.p.m. =3: 67 B.H.P. (maximum lift).

Machine, Centrifugal Pump, 8 in. Outlet,

Drive, Direct, by 20 B.H.P. Motor, 800 r.p.m.

Work, 5 tons per minute, 32 ft. head = 23 B.H.P.

Machine, Centrifugal Pump, 5 in. Outlet {for Condenser Water),
Drive, Direct, by 4 B.H.P. series motor, 750 r.p.m.
Work, 2 tons per minute against 12 ft. maximum heads
325 B.H.P.

Machine, Vertical Shaft Turbine Pump, for Raising Condensing

Water from the River,
Drive, By cast-iron bevel gear.
Motor, 5 B.H.P. series, 600 r.p.m.
Turbine, Speed, 350 r.p.m.
Work, Raising 6 tons per minute against 10 ft. head (maximum)

B.H.P. taken = 515 when the head was 5 ft.

Class VII. — Cranes.

As there are 157 cranes of sizes from i^ to 100 tons, it is quite
mpossible to descrit)e many of them. A few of the most important
only are described.

The Table below gives the average ratios of H.P. to lifting capacity

Class of Crane.

Motor B.H.P. per Ton Ufting Capacity.

Lift. Long Traverse.

Cross Traverse.

Melting House

Foundry

Forge

Gun Shop (Heavy Guns),
17 Cranes

Armour Plate Planing Shop

Armour Erecting Shop ...

Light Machine Shops

2 Tons Electric Lifts

7
•4

•8

•6
•5
•4

•25
Single Motor—
•375

1*2

Single Motor

•25
•20
•17

•13

•5 B.H.P per ton.

•2

•4

948 WILLIAMSON : APPLICATIONS OF ELECTRICITY [May 7th.

in different shops. The figures are not by any means adhered to in all
cases, many cranes of intermediate lifting capacity having motors a
size larger or smaller than the average ratio dictates, for the sake of
interchangeability. The ratios stated simply show average values
which give satisfactory service under the various conditions.

Number of Motors per Crane, — In most cases there are three motors,
one to each motion, although some of the earlier rope-driven cranes
were converted to -electric cranes by attaching one motor to drive the
three existing motions. Experience of both types has proved that the
cost of upkeep is less with three motors than with one, and the efficiency

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iimmniiiMMi

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s-sopm.

Z'i&p.m.

is greater. On some of the heaviest cranes five motors are used, there
being two crabs, one for light work, to avoid having to lift small
weights at the comparatively slow speed limiting the motor of the
heavy crab.

In connection with the average current taken by a number of
cranes, the diagram (Fig. 2) is of interest. It represents the curve
drawn by a recording ammeter in a circuit serving 7 cranes, with 21
motors of a total B.H.P. of 397. This is the largest number of cranes
on any single circuit, and the curve only shows to a small extent the
tendency of a number of cranes to provide a uniform load. As a
matter of fact, although some of the single cranes take 400 or 500
amperes to start them, there is hardly any sudden fluctuation observable

1903.] IN ENGINEERING AND SHIPBUILDING WORKS.

949

on the main ammeters in the power-house. Fig. 3 shows the record of
a single 20-ton 3-motor crane. The average speeds of the different
motions are as follows —

Feet

per Minute.

Lifting.

Long. Travel.

Cross Travel

5 Tons Crane ...

300

10 „

250

20 „ „

200

60 „ „

150

jQOdimas.

The largest crane is a 100-ton crane by the Wellman-Seaver
Company of America, in the steel melting house. The span is
46 ft. 6 in., and there are five motors of 260 total B.H.P. in the
following units : —

Main Crab, Lifting
Auxiliary Crab, Lifting ...
Main Crab, Traverse
Auxiliary Crab, Cross Traverse
Longitudinal Travel

Weight of crane and motors

Motor B.H.P.

Feet

per Minute.

. 100

. 50

. 25

• 5

100

. 50

150

)rs =s 140 tons

All motors are tramway type, and all controllers are of the com-
mutator t3rpe with magnetic blow-out and iron strip resistances.

Another crane of particular interest is a 60- ton crane in the armour-
plate shop, used for dipping the plates in the oil bath. Here it is
necessary to lower the hot plate quickly, and accidents have occurred
through too quick lowering with the ordinary type of crane bursting
the bands of the armature. Any stopping of the plate when half
immersed means firing the oil in a tank about 30 ft. deep.

»50 WILLIAMSON: APPLICATIONS OF ELECTRICITY [May 7th,

The old 3-motor crane was transferred to another shop and replaced
by a 4-motor crane with the following motors : —

Lifting ...
Travelling
Cross Traverse
Pump Motor

45 B.H.P.

8 „

4 n

One end of the lifting-rope is wound on a barrel driven by the 45 H.P.
motor, the rope then passes over a sheave on the trolley down to the
lifting-hook, then up over another sheave on the trolley and along to

§00

Fig. 4. — Brown Hoisting Co.'s Cantilever Crane.

the end of the crane-girder where it passes several times over sheaves
attached to a hydraulic cylinder and ram. Before lifting, the cylinder
is pumped full of water, and the ram is forced out to its full extent ;
lifting is done by the 45 H.P. motor, and lowering is performed as
quickly as desired by allowing the water to escape from the cylinder.

Another crane of exceptional interest is that used for the transport
of iron ore from the stockyard across the River Don to the railway-
within the works. The span across the river from track to track is
187 feet, and the overall travel of the trolley is 360 feet, extensions at
either end being carried on the cantilever principle.

The three motions for lifting, travelling, and cross-traversing are
driven by a series-motor of 85 B.H.P., through clutches ; the controllers

1908.] IN ENGINEERING AND SHIPBUILDING WORKS. 961

are of the tramway type, and the whole is operated by one man in a
cab attached to one of the travelling carriages. The height of the
trolley rails above water level is 47 feet.

The following readings were taken immediately after erection, when
the motions were naturally a little stiff : —

(i) Travelling 80 feet per minute.

„ starting ... 75 B.H.P.

„ running ... 44 >»

(with 5 tons on hook.)

(2) Trolley travel 1,000 feet per minute.

Starting 64 B.H.P.

Running 32 „ .

(3) Hoisting 400 feet per minute.

Starting 100 B.H.P.

Running 100 „

The curve (Fig. 4) shows the current taken (at 200 volts) when
lifting a weight of 5 tons, transporting it across the river and lowering
it into a railway truck. There are four similar cranes at the Barrow
Shipyard, two over the building berths, and two in the plate and
stockyards. The motors are of the same power, and the arrangements
generally are similar except that the overhangs are much longer.

The ship cranes are 320 feet overall, and run on trucks about 730
feet long and 80 feet above the ground, carried on steel gantries.
They will lift 15 tons, and the speeds of the respective motions arc
stated below.

Lifting 15 tons 125 feet per minute.

»> 7t ff ••• ••• ••• 3^^ n *f

»» iton 700 „ „

Trolley travel 400 to 800 „ „

Crane „ 400 to 700 „ „

These cranes are of the greatest service in accelerating the building
of ships and placing the armour.

Class VIII.— Metal Saws.

Machine. Armour-Plaie Sawing Machine,
Drive, Cut steel spur gear.
Motor. 5 B.H.P., shunt, 600 r.p.m.
Wotk, Sawing 2^ in. thick armour-plate.

One saw 38 in. diameter x f in. thick.

Speed of saw teeth 13*5 ft. per minute.

Rate of cutting, 9 in. per hour.

Power taken = 3 B.H.P.

Machine, Double Armour-Plate Saw,
Drive. Belt from motor to machine.

952 WILLIAMSON; APPLICATIONS OF ELECTRICITY [May 7th,

Motor. 10 B.H.P., shunt, 6oo r.p.m.

Work. Sawing two plates, 2^ in. and 2 in. thick respectively.

Speed of saw teeth, 157 ft. per minute.

Rate of cutting plates, 6 in. and 10 in. per hour
respectively.

Power taken = 7 B.H.P.

Machine. Crank Web Sawing Machine.

Drive. Four reductions from motor to saw by steel spur gear.

Motor. 2i B.H.P., shunt, 900 r.p.m.

Work. Sawing out web of locomotive crank 13 in. deep.

Two saws in use, each J in. wide, 47 in. diameter.

Speed of saw teeth = 10 ft. per minute.

Rate of cutting (each saw), 3*6 in. per hour.

Power taken = 2*25 B.H.P.

15 lbs. of steel removed per B.H.P. hour.

Machine. Band Saw.

Drive. By Renold chain.

Motor. 3 B.H.P., variable speed, 600 to 900 r.p.m.

Work. Sawing steel ingot, 14 in. deep, saw Vj in. thick.

Speed of saw 132 ft. per minute, feed i in. per
minute =s '90 B.H.P.

Class IX. — Wood-working Machines.

Machine. 35 in. Circular Saw.
Drive. Belt from motor to saw, 3 to i ratio.
Motor. 15 B.H.P., shunt, 600 r.p.m.
Work. Cutting 10 in. teak about 8 ft. per minute.
Power taken = 14 B.H.P.

Note. — Belt slipping prevented a higher speed of cutting ;
with a better drive a 20 H.P. motor would be required.

Machine. 24 in. Circular Saw {portable).

Drive. Direct from motor spindle.

Motor. 4 B.H.P., shunt, 1,500 r.p.m.

Work. Sawing 6 in. beech 4 ft. per minute = 4 B.H.P.

Sawing 2 in. white pine 10 ft. per minute = 275 B.H.P.

Saw running light = '55 B.H.P.

Machine. Band Saw {Driving-wheels 36 in.). Saw ^ in. wide.
Drive. By Renold chain. (Saw speed 3,670 ft per minute.)
Motor. 2 B.H.P., shunt, 1,000 r.p.m.
Work. Sawing 3^ in. Kauri pine = 143 B.H.P.

Sawing 9} in. Kauri pine = 2*8 B.H.P.

Sawing 7^ in. yellow pine = 1*63 B.H.P.

1903.] IN ENGINEERING AND SHIPBUILDING WORKS. 963

Machine. 24 in. Circular Saw.
Drive. Belt, speed of saw 1,000 r.p.m.
Motor, 10 B.H.P., shunt, 600 r.p.m.
Work, Cutting 5 in. ash, about 10 ft. per minute.
Power taken = 6 B.H.P.

Machine, Sawmill Circular Saw (to take 60 in, diameter Saw).
Drive. Belt, speed of saw 750 r.p.m.
Motor, 30 B.H.P., shunt, 600 r.p.m.

Work, Sawing damp pitch pine 12 ft per minute, thickness
from 10 to 17 in. (average 14 in.).
f Maximum, 36 B.H.P.
Power taken -I Minimum, 21 B.H.P.
( Mean, 26 B.H.P.

Machine, Grating Saw.

Drive, Belt.

Motor. 10 B.H.B., shunt, 600 r.p.m.

Work. Cutting 4 grooves ij in. wide x i in. deep in teak.

Speed of cutting, 2 ft. per minute.

Running light, 2^ B.H.P.

Grooving, 10 B.H.P.
The drive is a bad one, with jockey pulleys for the belts.

Machine. Wood Planing Machines (36 in. wide).
Drive, Belt.

Motor. 10 B.H.P., shunt, 600 r.p.m.
Work, Planer running light, 2^ B.H.P.

A in. cut off 27 in. wide pine 14 ft. per niin. = 8 B.H.P.

^V in. cut off 12^ in. wide teak 14 ft. per min. = 6 B.H.P.

J in. cut off 22| in. wide teak 14 in. per min. = 7 B.H.P.

Machine. Wood Moulding Machine.

Drive. Belt.

Motor. 10 B.H.P., shunt, 6od r.p.m.

Work. Cutting teak about 5 in. square on three sides and

ploughing fourth side, moulding passing through

13 ft. per minute = 105 B.H.P.

Machine. Wood Planing Machine (24 in, wide).
Drive, Belt.

Motor, 5 B.H.P., shunt, 600 r.p.m.
Works. Planer speed, 2,200 r.p.m.

Planing 16J in. pine i in. cut, 14*5 ft. per min. 3= 3*25

B.H.P.
Planing 16J in. pine ^\ in. cut, 14*5 ft. per rain. =s 2*5

B.H.P.
Planing 14 in. pine ^ in. cut, 14*5 ft. per min. =3 B.H.P.

964 WILLIAMSON: APPLICATIONS OF ELECTRICITY [May 7th,

Class X. — Special Machines.

Wellman Charging Machine for Steel Furnaces,

This machine consists of a carriage running alongside the furnaces
on rails 12 feet gauge, having the following motions : —

(i) Longitudinal motion on the rails, 25 H.P. tramway motor.

(2) Cross traverse of the crab or charging platform, driven by a

25 H.P. tramway motor. This crab carries the operator and
all the controllers, with the two other motors.

(3) Raising the porter bar which lifts the charge of metal in

special tubs, 25 H.P. tramway motor.

(4) Turning gear for turning the bar and tubs over, to empty the

charge into furnace, 5 H.P. enclosed motor. All motors drive
through steel cut gears.

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Fig. 5.

The method of working is as follows : — ^The operator runs the
charger along until opposite the furnace door. He then runs the bar
forward and lowers it into the slot in the end of tub, which is placed
ready on a trolley with others, making the complete charge. The bar
is lifted, and when high enough it is run forward into the furnace and
turned over, discharging the metal into the furnace. The bar is then
withdrawn, and the next tub is emptied in the same way. Two
chargers are in use, one on each stage of the melting house.

Power, charging tubs each containing 3 tons, average = 7 B.H.P.
Maximum observed , 40 B.H.P.

1903.] IN ENGINEERING AND SHIPBUILDING WORKS.

955

It is interesting to compare the cost of charging a 40-ton Siemens
furnace by the Wellman charger with the cost of charging by manual
labour. Under the former conditions'of hand-charging it was necessary
to have four highly paid men per furnace, whose earning depended on
the tonnage of output ; also there were additional helpers kept to give
occasional assistance in handling heavy pieces of scrap. The time
taken to charge 40 tons was four hours. Now two men are employed
in place of four, and the same operation is performed in half an hour,
or one-eighth of the former time. (For recording ammeter diagrams,
see Fig. 5.)

The output is naturally increased very largely. One man, taken
from the ranks of the labourers, made a skilful operator on the
Wellman charger with a few days' training, and he attends to six
furnaces. The furnace men are relieved of much of the laborious part
of their duties, and are at liberty to give better attention to the more
skilful part of their work. Also, in the hot part of the year the output
is the same as in cool weather, while formerly, with hand-charging, a
reduced output was accepted as a natural consequence of hot weather.

Summing up the advantages, we have a reduction in the wage costs
of melting of 50 per cent., with an increase in the output of 25 per cent.,
and the life of the furnaces is considerably extended, consequently
repairs are lighter.

The 40-ton charge by the Wellman charging machine takes three
Board of trade units at 075d. = 2jd. for power.

Hand Charging.

Electric Charging.

Capacity of furnace

Time taken

Men engaged per furnace

Wages per ton

Electric power

Charges per furnace per week ...

40 tons

4 hours

4 -H occasional

help

2S. 8d.

40 tons

i hour
2 + ith of the
operators' time

IS. 3d.

2jd.
12

Trepanning Machine, (Two Trepanning Bars,)

For boring ingots and gun tubes, leaving a solid core,
revolves.

The bar

Drive, Spur geariqg.

Motor, 15 B.H.P. variable-speed shunt motor, 250-500 r.p.m.

Work, Boring two 6 in. " B " tubes in one piece.

The end of each bar carries 8 tools. (Ordinary tool

steel).
Diameter of hole = 9f in., feed 3 in. per hour each bar

= 124 B.H.P.
Pump for washing out boring driven by a 5 B.H.P.
motor.

966 WILLIAMSON : APPLICATIONS OF ELECTRICITY [May 7th,

Another Test, with Vickers High-Speed Tool Steel.

Machine, Similar to the above, but with only one bar.
Motor, 2$ B.H.P., variable speed, 300 to 900 r.p.m.
Work, Boring a 14" hole in steel ingot.

Rate of feed, loj^" per hour.

Power taken = 22 B.H.P.

A similar machine (single bar only) trepanning a 2it in. hole in a
steel ingot takes 10*9 B.H.P.

Feed = 2^ in. per hour. (Ordinary tool steel).

Hauling Crab for Furnaces,

A fixed crab, driven by a 5 B.H.P. motor through spur gear, hauls
the car carrying armoiu* plates into and out of the furnace
by endless chain engaging in sprocket wheels.

Six-wheeled car, carrying 36 tons of plates hauled at

the rate of 30 ft. per minute.
Mean power taken = 5 B.H.P.
Maximum „ = 5*25 B.H.P.

Manganese Crusher,

Belt driven from 10 B.H.P., shunt motor, 600 r.p.m.
Running light = 2-5 B.H.P.
Crushing = 9 B.H.P.

Brick Crusher.

Driven by belt from 10 B.H.P. motor, 600 r.p.m. (shunt).
Work, Crushing old bricks and furnace linings for concrete.

Running light = 175 B.H.P.

Crushing = 95 B.H.P.

Mortar Mills,

(a) With driven rolls and fixed tray.

Belt driven from 10 B.H.P. shunt motor, 600 r.p.m.
With tray full of mortar = 12*5 B.H.P.

(b) With fixed rolls and driven tray.

Belt driven as (a)

With tray full = 9 B.H.P.

Power Hammer, 5 cwt, size.

Vertical hammer with pneumatic cushioning.
Belt driven from 10 B.H.P., shunt motor, 600 r.p.m.
Work. Hammering out wedges for shipyard use, about
6 in. X 8 in., i in. thick tapered to nothing.

Hammer striking = 475 B.H.P.

Cushioning = 9 to 10 B.H.P.

1903.] IN ENGINEERING AND SHIPBUILDING WORKS. 957

Note, — A series motor would be better for the work, about 5 B.H.P.
It would drop its speed when cushioning, and not take more
than about 6 or 7 B.H.P.

Stern Tube Boring Machine.

Starboard tube of H.M.S. Hogue,

8 in. diameter bar driven by a worm-wheel and worm, which is

driven by a 10 B.H.P. shunt motor, 600 r.p.m., through

chain gear and bevel wheels.
Speed of bar, 1*36 r.p.m.
Diameter of hole bored, 26J in.
Cutting speed of tools, 9-5 ft. per minute.
Running bar light = 2 B.H.P.
Four tools cutting x\ in. = lo'i B.H.P.

Armour-Plate Grinders.

There are seven of these machines, each consisting of a long bed on
which travels a saddle carrying the grindstone and motor. The motor
spindle is extended through a heavy bearing, and carries the chuck into
which segments of grindstone are wedged. The speed of motor and
grindstones is 400 r.p.m. The motors are of two sizes, 20 B.H.P. and
40 B.H.P., with good overload capacity. The work consists of facing
up the edges of armour plates, which to a certain depth are too hard to
be machined in a planer. The thickness of plate varies from 2 inches to
12 inches, and the power taken varies from 20 to 60 B.H.P. It is very
easy to overload the motors, a slight movement of the feed-wheel
presses the grindstone hard against the work, and the current sometimes
rises to the equivalent of 80 B.H.P. Heavy fuses are found better than
overload release starters, as they are not too sensitive, and by becoming
red-hot warn the grinder to ease his cut.

Class XI. — Fans and Blowers.

Steel Foundry Converter Blowers, (Roots.)

Capacity of converter, 2 tons.

Blower direct driven by 75 B.H.P., shunt motor, 500 r.p.m.

Pressure In Converter. RH.P.

1*5 lbs 40

175

2*0

225

2*5

45*5
48-25
53-5
615

Iron Foundry Cupola Blowers, {Roots,)

Charge melted per hour, 8 tons (maximum possible, 9 tons).
Blower driven direct by 75 B.H.P. shunt motor, 500 r.p.m.

Pressure in Cupola. B.H.P.

Running light 23

14 ozs. 70

^5 n 73

Vol. 32. 64

968 WILLIAMSON: APPLICATIONS OF ELECTRICITY [May 7th,

Iron Foundry Cupola Blowers, {Roots,)

Charge melted per hour, 3 tons (maximum possible, 4 tons).
Blower belt-driven by 40 B.H.P. shunt motor, 500 r.p.m.

Pressure in Cupola. B.H.P.

9 ozs 34

9* » 35'5

10 „ 37

Steel Foundry Cupola Fan, (Siurievant.)

Charge melted per hour, 2 tons (maximum possible, 4^^ tons).
Belt driven by 20 B.H.P. shunt motor, 600 r.p.m.

Starting 16 B.H.P.

Running light 11 „

Blowing 12 „

Fan for Smiths* Fires.

1,400 revolutions per minute, belt driven from motor 5 B.H.P.
600 r.p.m.
Work — 9 fires.
Load— average 5 to 55 B.H.P.

48 in. Fan with 20 in. x 20 in. Outlet.

Belt driven at 1,000 r.p.m. by a 10 B.H.P. shunt motor, 600 r.p.m.
Work — 23 smiths* fires and air blast for chemical laboratory
= 8-5 B.H.P.

Roots Blower— No. 2 " 1900 " Pattern.

Driven by belt from 10 B.H.P. shunt motor, 600 r.p.m.
Work — 8 fires -|- heavy lead melting-pot.
Speed of blower = 190 r.p.m.
= 6-4 B.H.P.

Portable Air Compressor {for Working Pneumatic Chippcrs).

Size of compressor, 4 cylinders 10 in. diameter x 6 in. stroke.

Drive — Spur gear.

Motor — 15 B.H.P., shunt, 350 r.p.m.

Air pressure — 70 lbs. per sq. inch.

Work — 6 chipping tools or 3 drills.

Power = 15-3 B.H.P. ^

Portable Painting and Lime-washing Machine,

Works two paint sprays.
Motor — 2^ B.H.P., shunt, 1,200 r.p.m.
Speed of compressor — 102 r.p.m.
Gear—Worm, sinf^le reduction.
Air pressure — 10 lbs.

' Power = 2-6 B.H.P.

1908.] IN ENGINEERING AND SHIPBUILDING WORKS.

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960 WILLIAMSON: APPLICATIONS OF ELECTRICITY [ May 7th,

The following tables stating the brake H.P. of motors and number
of watts consumed per i,ooo feet of shop area maybe of use in forming
an idea of the probable size of plant required to drive works of a similar
nature.

The figures dealing with plant installed do not vary with the state
of trade, busy or slack, as do the figures relating to the current con-
sumed per B.H.P. installed, which are also stated in tabular form. It
should be noted that in all cases the figures of current per B.H.P. of
motors relate to times of normal trade, and a margin should be allowed
to cover the possible requirements during times of extra pressure.

B.H.P. OF Motors Installed per i,ooo Square Feet of
Shop Area.

Sheffield, North Gun Shop (Heavy Guns, 6 in. to 12 in.)

South „ ( „ „ )

East „ (Gallery over alternate bays, 47 in.
Guns)

Armour Plate Planing Shop

Barrow, Shipyard Platers' Shed

Woodworking (Joiners and Blockmakcrs)

Engine Department Machine Shop

Gun Mountings and small work

Erith, 6 in. Gun Mounting and Carriage Department (Gallery
over alternate bays)

Gun Turnery

Woodworking Shop (two stories)

Wolseley Motor Car Company Lid. (all small power machines) ...

12-8

13*4

I2-0
15-4

43
3*9

44
43

745
3*4
6-5
172

Average Current and Watts (at 220 Volts) taken per B.H.P. of
Motors Installed.

Sheffield. North Gun Shop

South Gun Shop (average of 5 circuits)

East Gun Shop

Railway Axle, etc., Turnery

Cranes in Gun Shops (eight 60-ton

cranes on the ci rcuit)

Barrow. Shipyard Platers' Shed

„ Woodworking Shop
Engine Department Machine Shop ...
Gun Mounting and small work bays...
Erith. Whole Works (Guns and Gun Mount-
ings small)

North Kent. Field Gun Carriages, etc

Current.

Watts.

1-2

... 264

136

299

1*02

.. 224

1-27

279

1 10

1*05

.. 231

163

.. 358

206

•• 453

176

392

1-15

253

1-8

.. 396

1903,] IN ENGINEERING AND SHIPBUILDING WORKS.

Current.

Electric and Ordnance Accessories Company, Ltd,

(at no volts)

The current and watts required at 220
volts to give I B.H.P. with an
average efficiency of 80 per cent,
(allowing for motors working
slightly uhder full load) are ...

4-24

961

Watts.
550

932

Total Number op Arc and Incandescent Lamps.

16 c.p. Incand

Sheffield

558

3>5oo

Barrow

720

4,000

Erith

400

3,500

North Kent ...

400

Wolseley

750

Electric and Ordnance

e ... :.. 48

900

1,866

I3I050

Total Number and H.P. of Cranes — Electrically Worked.

No. of Cranes.

B.H.P. of Motors.

No. of Motors.

Sheffield ...

... 89 ...

2,683

170

Barrow

1,542

145

Erith

216

157

4,441

348

Number of 500- Watt Arc Lamps and Kilowatts per 1,000
Square Feet Shop Area.

Sheffield, North Gun Shop

South Gun Shop

East Gun Shop

Armour Plate Planing Shop

Marine Crank Turnery

Railway Crank and Small Machine Shop.

Iron Foundry

Steel Melting House

Forge

Repairing Shop

Boiler Shop

Barrow, Shipyard Platers' Shed

Woodworking Shop

Engine Department Machine Shop

Boiler Shop

Iron Foundry

KiUowatts.

Number.

. -448 ...

•90

. -401 ...

•80

. 360 ...

. 320 ...

•64

. -390 ...

•78

. -250 ...

•50

. 234 ...

•47

. 257 ...

•51

. 320 ...

•64

. -330 ...

•66

. -356 ...

•71

. -310 ...

•62

. -275 ...

•55

. -375 ...

•75

. -35 ...

•70

. -21

•42

KUlowatta.

Number.

•25

... 'SO

•45

... 9

... 14

•68

••• 1-37

•68

... 136

•46

... 92

•376

- 755

962 WILLIAMSON: APPLICATIONS OF ELECTRICITY [May 7th,

Steel Foundry

Gun Mountings and small work
Erith. 6 in. Gun Mounting and Carriage Depart-
ment*

Gun Turnery*

Mechanism and Shell Department *

Field Carriage Erecting Shop
Wolseley Tool and Motor Car Co., Ltd

Average Figures.

Heavy machine shops (average height of lamps = 35 ft.) = 400

watts per 1,000 sq. ft. of floor area.
Light work (average height of lamps = 16 ft.) = 375 watts per

1,000 sq. ft. of floor area.
Foundries and steel melting = 240 watts per 1,000 sq. ft. of floor

area.
Forge, about 350 watts per 1,000 sq. ft.

These figures vary considerably with the amount of reflection which
the walls provide and the possibility of keeping the walls clean.

Although a great deal might be written on the subject of starting
gear, switchboards, tjrpes of arc lamps, fuses versus circuit breakers
and many other points all of importance to those interested in the use
of motors, the author feels that this paper is sufficiently long without
reference to most of them. It would be interesting to hear some
experiences of engineers with circuit breakers fitted in such power
installations as those described in this paper.

The author has a preference for starters without automatic overload
release, and has had to do away with the overload release on a number
of starters which were continually giving'trouble by switching off when
overloaded momentarily. The time-constant of a fuse is a very strong
I>oint in its favour, as it will carry a motor over a heavy load of short
duration which would at once open the automatic. Also, a fuse's
sensitiveness is not affected by vibration, as is the case with most of
the automatic overload arrangements. If automatic circuit breakers
are fitted on the generator panels, they should also be fitted to feeder
panels and to all motors, as the presence of even a small fuse may cause
a very large generator to come off load before the fuse has time to melt.

Saving due to Electric Driving.

As the available figures under this head have been published fre-
quently, it will be as well to keep entirely to results obtained by the
Vickers Company. The difficulty of stating the saving in terms of
simple comparison is very great. When a concern takes up electric
driving in earnest, it usually finds that many operations become possible

• An attempt was made here to light entirely by arc lamps, but for the fine
machining and fitting incandescent lamps are found necessary.

1903.] IN ENGINEERING AND SHIPBUILDING WORKS. 968

^Krhich were not possible before ; consequently new machinery is
ordered.

The author does not know a single instance where the conditions of
working were the same before and after conversion of works to electric
driving.

At Barrow, as already stated, an extension of the shipyard, approxi-
mately equal to 50 per cent, increase in the power taken, marched hand
in hand with the conversion to motor driving. Also, electric lighting
had been largely extended. The actual result was a saving of half the
coal bill, with an increase of over 50 per cent, in output. In no other
instance is it possible to express so direct a comparison.

Where boilers have been relieved of a part of their load through
motor driving, the steam set at liberty has been used for other purposes,
such as working additional hammers, presses, or other hydraulic
plant. '

It is disappointing to find that the saving, which is so thoroughly
evident to those who use electric driving, cannot be more clearly stated.
It is only by considering such cases as the charging machine, where
much labour is dispensed with, that an idea can be formed of the
magnitude of the saving in works where there arc many instances of a
similar kind.

In the armour-plate planing shop, now driven by three engines
developing over 600 B.H.P., motors are being installed. There will
be a saving of six engine drivers (one to each engine on day and night
shift), against which there will only be a proportion of the wages of one
engine driver in the power-house to be charged. In this shop, which
has six cranes of 60 tons lifting capacity, recently converted to electric
driving by fitting six single motors in place of 5,200 feet of ropes, a
saving of ;£i8o per annum has been effected under the head of rope
renewals alone. A very large saving is also made by cutting out the
constant loss due to keeping the mile of rope running, and the rate of
handling the heavy weights has been doubled. Formerly the repairs
to the rope pulleys and running gear formed a very heavy item.

The number of stand-by men in works dealing with heavy weights
can be greatly reduced by the judicious use of motors. A few years
ago it was usual to keep a gang of men to do such odd jobs as opening
furnace doors, and on the large furnaces six men were required to raise
some of the heavy doors. Now this operation is performed by a i^ H.P.
motor, and only as many men are employed as can be kept fairly busy.

The author thinks that the future applications of motor driving will
be largely in the direction of doing all the rough, heavy work, which is
now left to labourers through the shortsighted policy of many employers
who will not see that the outlay on motors is soon recovered. A man
can do work which a motor cannot, and he should be set free to do
that work. As a machine he is not very efficient The spectacle of six
ordinary men pulling on the fall of a rope in as many different directions
proves this fact.

The author wishes to express his indebtedness to Messrs. Vickers,
Sons & Maxim, Ltd., for their kindness in allowing him a free hand in

964 CHATWOOD : ELECTRIC DRIVING [May 7th,

publishing the figures in this paper, and also to the following gentlemen
for assistance in taking the various tests : —

Mr. C. L. Sumpter,
Mr. H. R. C. Partridge,
Mr. E. F. Long,
Mr. W. R. EUison,

and to Mr. C. Salmon, of the Erith Works, and Mr. R. F. HaU, of the
Electric and Ordnance Accessories Co., for the figures relating to their
respective works.

yj ELECTRIC DRIVING IN MACHINE SHOPS.

By A. B. Chatwood, B.Sc, Member.

The subject of electric driving has of late years received consider-
able attention, but there seems to be a great deal of misapprehension
in the public mind as to the attitude adopted by electrical engineers in
the matter. The author has frequently been told by managers and
principals of works that they would wait until electrical engineers had
come to some conclusion as to which was the best system and the best
method.

Discussions have taken place in this room and elsewhere as to
whether direct or alternating current was the more suitable for tool
driving, as to whether the final solution of the problem would be one
motor per tool or one motor per line shaft, and so on. Whatever value
such discussions may have in the abstract, the author is of opinion that
in each particular case of machine tool driving electrical engineers
would have substantially the same views, and he therefore proposes to
leave all discussion of abstract points alone, and to ask the attention of
members to three particular cases, out of those which have come
closely under his own observation, and to the conclusions to which
they lead.

There are, however, a few general questions to which attention may
very well be drawn at this point.

Wherever possible, it is desirable to employ direct rather than
alternating current, as speed control is of extreme importance with
regard to some classes of engineering tools.

The system and voltage to be employed should be such that the
installation may either permanently or temporarily be connected to the
town mains.

Where, for any reason, a qualified electrician cannot be maintained
on the staff, the installation should involve only apparatus which is
well understood in the district, so that help or advice can always be
readily obtained.

As a general rule it will, the author thinks, be wise to group tools
together for driving purposes to a very large extent, but at the same

1903.]

IN MACHINE SHOPS.

965

time to drive certain classes of tools individually. The average number
of tools per motor is difficult to arrive at, but in engineering shops
doing partly standard and partly odd work of medium weight, the best
number will probably work out at from two to four.

The particular cases which it is proposed to submit are those of two

■D

MMiiiia«IHIIIfiiiiprif?

»*>

.□

Fig. I.

old and one new works, all of small size. Plans of all three are
shown.

In Bolton, where these shops are situated, direct current is supplied
on a three-wire system at 460 and 230 volts, and motors may, under
certain circumstances, be hired from the Corporation at 10 per cent.

966 CHATWOOD: ELECTRIC DRIVING [May 7th.

per annum on the cost of motor, starting switch and fixing, the price
of energy being as follows : —

First 500 units per quarter 2*25d. per unit

Second „ „ r35d. „

Further consumption I'ood. „

The author proposes to take these terms for interest and deprecia-
tion, and these prices for current, as a basis for the estimates in the
present paper.

Case I.

Until May, 190 1, the shop shown in Fig. i was driven by a Robey
portable made at a very early date, and by a small single-cylinder
horizontal with vertical boiler placed in the smithy.

At this time the engines were entirely worn out, and in fact for
some years previously the repair bill had been enormous, so that it
was decided to adopt electric driving, and a 20 B.H.P. motor was in-
stalled in the position shown on plan. The shop has since been driven
by this motor, with results which are entirely satisfactory except as
regards cost and occasional stoppage.

The actual mean load, including shafting, was 15 H.P., and the cost
of steam driving somewhat as follows. Owing to the fact that no
proper cost books are kept in this works, these figures may be one or
two per cent wrong either way : —

Wages

Coal

Water

Ash removal

Oil

Repairs

213

'£37^

for a year of about 2,800 working hours, or about ;£434 for a year of
3,194 hours. These figures are exclusive of interest or depreciation.

The cost of the single motor drive, at the present rates for current
is ;£i86 7s. 2d., as follows : —

10 per cent, on motor, etc.

Cleaning

Brushes

Current

£>

164

;£i86 7 2

1903.] IN MACHINE SHOPS.

The consumption for six months being as follows :-

967

Date.

Total Units.

Max. Current

Hours of Running.

June 19 to July 37

2,668

31 amps.

268-5

August 22

3»i40

32 ,,

2495

September 20 ...

3»i23

36 „

274

October 18

3,"9

36 „

295s

November 20 ...

3»i7o

35 ,»

249'S

December 20 ...

3,182
18402

32-5 »

269

i,S97

Mean consumption, 11-52 units per hour = 15*44 E.H.P.

Max. „ „ „ = 22*2 „

Measurements of the current required to drive the shafting alone,
including belts and loose pulleys, gave as mean figures : —

972 units per hour ....
We have therefore in this case-
Useful load

Waste load

12-9 E.H.P.

2-54 E.H.P.
12-9 »

even if we assume, which is certainly not true, that the shafting, etc.
absorbs the same amount of power when loaded as when unloaded.

You will notice that the motor drives a cross-shaft A, which in its
turn drives at one end a line shaft B, and at the other end an inter-
mediate B' ; each of these drives a second shaft C C, and each of these
again drives machine counter-shafts or in some cases another inter-
mediate D'.

This arrangement is not such as would be put up to-day by any
self-respecting engineer, but it is typical of a very large class of works
which have grown little by little, and in which a machine and a piece
of shafting have been tacked on from time to time; sometimes the
machine being put in an awkward position for the convenience of the
drive, and sometimes the drive being awkward for the sake of the
machine.

Case II.

At the present time the shop shown in Fig. 2 is driven by a single-
cylinder condensing beam engine of 6 ft. stroke and 25 in. diameter
cylinder. Some time ago I had the pleasure of reporting on the electric
driving of this shop. The particulars of the loads are as follows : —

CHATWOOD : ELECTRIC DRIVING

1903.]

IN MACHINE SHOPS.

969

Mean load

Max. „

En/^ne and shafting friction

266 I.H.P.

34-40
22

Mean useful load 4*6 „

with the same assumption as before with regard to the power absorbed
by loaded shafting.

The coal bill was about £430 per annum, and the total engine costs
something like ;£6oo, or about ;f22 per I.H.P. per annum, exclusive of
rent, rates, taxes, insurance, interest and depreciation.

Observations were made over some weeks in order to determine
the actual intermittency of the tools, with the following results : —

Motor
Groups.

Sec page
979

Max. B.H.P.

Per cent, of time

Class of Machine or Group.

required for
Group.

Group Shaft
would run.

Plate stretching rolls

Saws

Drilling machines

Milling and slotting machines ...

» »> »

Small planing machines

„ „ special...

Large „ „

Lathes

Sheet metal machines

„ „

Brass-finishing machines

Odd brass machines

Small special lathes

Polishing laps and brushes

Drilling machine

„ „

Small machines

The shafting load estimated from an empirical formula, taking into
account diameter, length, speed, number of bearings, and number and
width of belts, is—

Diameter.

Length.

B.H.P. hours per 3,000 hours.

11,880
1,260

i»449
1,530
18,770
2,220
4,860
7,290

Inches.

3
3
3

4
2

225
2

Feet
41260

22-5
140
22

152
222

49,250 = 164 B.H.P.

970 CHATWOOD: ELECTRIC DRIVING [May 7th,

a figure which agrees very cipsely with what one would expect from
the indications of the engine.

Taking the shafting load at this figure, and the useful load at the
I.H.P. given by the engine, viz., 4*6 H.P., the cost of driving by a
single 40 H.P. motor works out at ;£264 12s. 6d.

£ s. d.

10 per cent, on installation 28 o o

Brushes and cleaning 5 10 o

Current ' 231 2 6

£26^ 12 6

As a matter of fact the drive is being divided over four motors ;
with what object the author fails to understand, since almost the whole
of the shafting is to be driven and no one of the advantages of electric
driving is to be secured.

The cost of driving in this way will be greater than that shown by
the single- motor arrangement. The estimate being —

;£ s.d.

10 per cent, on installation 40 o o

Brushes and cleaning 11 16 o

Current 239 17 6

£271 13 6
Case III.

The shop here taken as an example (see Fig. 3), unlike those already
given, has only been erected a few months, and ft had already been
decided to drive with current from the Corporation mains ; yet in spite
of this, the same want of intelligent appreciation of the conditions of
the problem are shown.

The works, as will be seen from the plans, consist of two shops one
over the other, and a moulding shop. The lower shop contains a smaU
planing machine, slotting machine, shaper, drilling machine, grindstone,
and several lathes, one only of which is in fairly constant use.

The business carried on is chiefly that of brass finishers, although
all sorts of repairs are done.

In the lower shop it is rare for more than one or two tools to be
working at one time, and more often than not only one lathe is in use.

The lower shop, of which we are at present speaking, is driven by a
5 H.P. motor, driving by belt on to a short shaft and thence by belt
on to the line-shaft running the length of the shop. The shafting is of
steel, and is run in self-adjusting bearings. It has been most carefully
installed, and absorbs little power ; with seven belts to counter-shafts,
including the driving of the loose pulleys this amounted to 1*05 B.H.P.
The motor, however, although by a well-known firm, absorbed 265
E.H.P., running entirely light at the time the experiments were made ;
this has since been reduced to 247 E.H.P. by an alteration of the
maker's adjustment of the brushes. The result is still not what ought
to be expected by a very long way.

The upper shop contains several small lathes and other small tools.

s. d.

o o

O lO

1903.] IN MACHINE SHOPS. 971

and it may be taken that three or four tools are as a rule in operation :
there are also a set of polishing brushes which run a small part only of
their time, and are driven independently by a separate motor.

The main drive in this shop is by a 6 H.P. motor belt connected to
a line-shaft

This motor when driving only the shaft, belts, and loose pulleys
absorbs 2*47 E.H.P.

The author has had observations made as to the time which the
motors ran : during the period of observation the polishing motor was
entirely idle, that in the lower shop ran 2275 hours per week of 53
hours, the top shop motor running full time.

This gives us a consumption of 160 units for driving shafting ; the
meter readings gave a total consumption of 174 units during the 53
hours : thus the energy actually used usefully was 14 units, equivalent
to a mean useful load of '36 E.H.P., or about 8 per cent, of the total.

The annual cost on the assumption that the conditions obtaining
during the period of observation are maintained during the year
will be —

10 per cent, on installation

Current

£6S o 10

These figures are exclusive of the cost of running the polishing
brushes and a small motor recently erected in the moulding shop.

As the improvement in the efficiency of the 5 H.P. motor is directly
due to the measurements taken by the author for this paper, it has not
been considered in the above figures, since there is no doubt that it
would under ordinary circumstances not have been made.*

Probably there is no problem in the everyday practice of engineering
which involves so many factors that can only be ascertained by tedious
observation in each case, or where this work is so amply rewarded.
Experience is no doubt of very great value, but if any one, however
experienced, shirks the trouble of making the observations which have
been referred to, the results which he will achieve will fall far short of
success.

In the early part of this paper certain general lines were laid down,
but it will be found in practice that those .conditions are frequently
incompatible, and the engineer, as in so many other cases, must make
a compromise.

It is seldom that all the advantages of the electric drive can be
secured in any particular instance, but with care those most essential
to any particular class of work may be obtained without too much
complication or loss of financial efficiency.

The possible advantages are : —

1. Reduction of waste load.

2. Positions of machines independent of shafting.

3. Speed of individual machines or groups independent.

• Since this paper \va«^ written the makers have been communicated with,
and at once offered to replace th? motor by a thoroughly efficient one.

972

CHATWOOD: ELECTRIC DRIVING [May 7th,

F/PST FLOOR PLAN

GROUND PLAN

Scale, of Feet,

Fig. 3.

1903.J IN MACHINE SHOPS. 978

4. Facility for using portable tools or magnetic chucks.

5. Convenience on occasional overtime.

6. The very partial nature of a breakdown and rapidity of repair.

7. Advantages connected with travelling cranes.

8. Absence of strains in roofs and consequent cheapness of con-

struction.

9. Facility with which power measurements may be made.

The importance which attaches to the reduction of waste load
depends largely on what is in the particular shop the original source of
power. If current is generated by the use of steam engines on the
premises, the saving made by reducing waste load is not at all pro-
portionate to the reduction of the load, as a large part of the cost of
generation is due to charges which do not increase in prop>ortion
to the load : when, however, current is obtained from an outside
source at a practically level rate, this reduction becomes of very great
importance.

In being able to place his machines so that they get the best light,
and so that as little as possible need be wasted in getting work to or
from them, the works manager is in a position to demand the maximum
both as regards quantity and quality from his men ; and he can see at
a glance whether or not machines are being kept in that state of cleanli-
ness which is essential if good work is to be done and if machines are
to depreciate little.

The advantages due to the control of the speed of individual
machines, both in improving the quality of the work and in increas-
ing the quantity turned out, have not been fully appreciated up
to the present ; speaking as a practical turner who has had experience
of both systems of driving, the author is in a position to say that not
only can better work be done but a very great deal more of it on a lathe
fitted with a separate motor and a shunt regulating resistance. It is
perhaps somewhat rash to estimate the extra output under this heading,
but on lathes and planing machines which are not doing repetition
work an increase of anything between 20 per cent, and 40 per cent, is
usually obtained.

There are two ways in which portable tools may be of very impor-
tant use : the first when the piece to be machined is of great weight in
proportion to the amount of machining to be done on it ; and the second
when several parts of the piece may be machined simultaneously so
that time may be saved.

It is not necessary to speak of the advantages pointed out as Nos.
5, 6, 7, 8 above, as these are either sufficiently well known or are obvious.

It may be pointed out that the possibility of the easy, rapid, and
accurate measurement of power which is afforded by electric driving is
valuable to the works manager, firstly, because the friction load of a
machine is a very reliable indication of the condition of the machine,
both as regards its cleanliness and its adjustments ; and secondly,
because the current consumption as given by a meter shows very clearly
whether or not the machine lis being worked up to its full capacity
or not.

Vol. 82. 66

974 CHATWOOD: ELECTRIC DRIVING [May 7th,

The smallest size of motor which it is ordinarily desirable to employ
depends to a large extent on " the taste and fancy " of the engineer ; the
voltage of supply, however, seems to fix the limit in ordinary cases : the
author does not hesitate with a pressure of 200-250 volts to employ
motors as small as i H.P., and where any great advantage is to be
secured thereby, motors of J H.P. It must not, of course, be lost sight
of that small motors are less efficient than larger sizes, and that there-
fore they should only be used where the saving or convenience which
can be secured by them outweighs their disadvantages and leaves a
large margin of benefit.

The general arrangements as to the number of motors used with
which the author is acquainted are : —

1. One motor per works : This replacing of a steam or other engine
by an electromotor is, to say the least of it, foolish, as a gas, oil, or
steam engine would always give a more economical and equally satis-
factory drive.

2. One motor per tool : This arrangement is, as a rule, not the best,
as although the cost of the current is reduced very greatly, it is at the
expense of interest and depreciajtion, and it is difficult to imagine an
engineering shop where all the tools would be benefited by speed
control other than that obtained by cones, etc., or where many tools at
any rate are not employed on standard work which enables them to be
grouped without loss of efficiency.

3. One motor per line-shaft : This arrangement leads to a certain
amount of economy in large works generating their own current, but is
decidedly bad where current is purchased at an approximately level
rate, as the substitution of oil or gas engines would give a still more
economical drive. In either case the advantages peculiar to electric
driving are not secured.

4. Mixed arrangement developed from No. 3 : In this arrangement
one motor per shaft is employed as far as possible without involving
long lengths of idle shafting, and a few tools may have separate drives
on account of their inaccessibility.

5. Mixed arrangement developed from No. 2 : This arrangement,
which appears to the author to be the only reasonable one, may be
described as one in which each tool having a large percentage of idle
time, or which would benefit by a variable-speed control more delicate
than that given by the usual mechanical means, has its own motor, and
the remainder are grouped, not in any hard and fast way as so many
tools per motor, but in larger and smaller groups in such a way that the
sum of the interest, depreciation, attendance, repairs and current cost
shall be a minimum.

Probably the best way of arriving at the arrangement last described
is to pick out those machines which require separate motors in order to
secure variable speed, then those which are idle for a large percentage
of their time, as it will very likely be possible to group some of these
without loss ; the remainder of the tools will very probably fall into
convenient groups, but if not, their grouping merely involves the
calculation of the cost of driving for two or three arrangements.

In grouping it should always be borne in mind that it is often

1903.]

IN MACHINE SHOPS.

976

possible to combine tools to form a group so that the shaft driving the
group need only run a proportion of the working hours of the shoj>.
Sometimes one man has a group of machines in his charge of which
only one or two run at any moment : a group is thus formed naturally,
and may be driven by a motor too small to drive all the machines of the
group at once.

There is no doubt that the more the drive is split, the greater will be
the total H.P. of the motors required, and so the capital cost, for the
help given by the inertia of the shafting, etc., to reversing machines
and to those liable to sudden variations of load, is reduced, and the

HJ?io

f^=j\.

PLATE STRETCHMQ ROLLS ik: PLATE.

SMALL PLANE SOeTuE'^

H,B

Fig. 4.

fact that a large number of machines having a variable load never
synchronise is also neglected.

The total power of motors required with a divided drive such as has
just been indicated will of course vary very greatly in different shops,
probably as much as from twice to five times the maximum useful load
of an engine driving the same shop.

The power absorbed by particular machines can only be ascertained
by actual measurement, the power stated by tool makers being some-

976

CHATWOOD: ELECTRIC DRIVING

[May 7th,

times many hundred per cent, wrong. The few powers given below have
been measured by the author on tools in actual work under ordinary
shop conditions : —

12 ft. X 4 ft. 6 in. planing machine... Diagram C. (Fig. 4).

Radial drill, holes to i J in J H.P.

6 ft X 30 in. planing machine ... 2-65 H.P. in reversing.

10 ft. 6 in. X 30 in. planing machine Diagram B. (Fig. 4).

Lathe 5^ in.

Lathe 9 in.

Drilling machine, holes to ) in.
Plate stretching rolls

... ( Up to -34 H.P., cutting

( heavy screw,
... ( '5 H.P. chasing thread

I on 2i in. gas-pipe.
... i H.P.
... Diagram A. (Fig. 4).

The connection between the tool and the motor is at present
receiving a good deal of attention, especially at the hands of American
tool builders, and large numbers of tools are being built with a motor as

DtAGRM Of PLANINQ'MACHINL OmvC

Fio. 5.

The magnetic clutch (solid black) is double-ended and slides on the worm
shaft with a float key. In the position shown, the train of gears A is connected
to the shaft by the clutch, which is in contact with the left-hand armature.
The gear train contains an idler — on the current being passed (by the
machine tappets) through the other end of the clutch, the latter slides into
contact with the armature attached to gear train B.

a part of the construction. But in dealing with old shops, the connec-
tion whether to group shafts or to individual tools has to be provided ;
more often than not without any serious stoppage of the work : in these
cases a belt connection to the group shaft, or to the existing counter-
shaft of the machine, will as a rule be found the most convenient,
though a raw-hide pinion and a spur wheel or worm gearing can
sometimes be employed and arc to be preferred.

There are, however, two classes of machine to which special con-
nections should be fitted, namely, machines which reverse periodically
and have large inertia, such as planing machines ; and machines of very
great inertia which absorb a very large power in starting, yet take
comparatively little power in running.

1903.] IN MACHINE SHOPS, 977

A most ingenious arrangement for driving the former class of
machines is already on the market, and the author believes is working
perfectly satisfactorily, the only objection to its adoption being that the
price is extremely high and is certainly not warranted by the cost of
manufacture. A diagram of this appliance is shown in Fig. 5.

The second class of machines which should have special attachment
is represented by the grindstone used in many works for removing
scale from bars, dressing of rivets, and for other purposes ; these stones
vary in size, but are usually about 7 feet diameter when new. Such a
stone absorbs, with the friction of its bearings, from 2^ to 4 H.P^ and
occasionally for short periods as much as 5 H.P. after it gets up speed,
so that a motor of 4 H.P. is amply sufficient to drive it, but it requires
one of at least 15 H.P., even when a few series turns are provided, to
start it if both have to start together ; and if the motor is allowed to get
up speed and the stone then coupled by anything approaching a rigid
connection, the motor, even if of 15 H.P., is extremely likely to be
injured, as it will be overloaded to an enormous extent.

To meet these difficulties and to provide for a constant peripheral
speed in spite of the wear of the stone, as well as for a low speed of
about 50 linear feet per minute when turning up, the author has pro-
posed a two-speed motor with a small controller and a shunt regulator
driving the stone through a belt, and the use of a magnetic coupling in
the shaft which carries the stone, or, if possible, in the motor shaft
between the motor and the pulley. The current supplying the clutch
passes through a rheostat, so that the power transmitted to the stone is
under control.

The method of operating this apparatus is extremely simple ; the
controller is turned to one or other of its two positions according to
the diameter of the stone, and the motor switch pulled over slowly just
as in starting a motor, but after the motor has acquired its speed the
switch is carried on, cutting out resistance in the clutch circuit and so
gradually transmitting more and more power to the stone. The
advantage of such an arrangement is that the stone can safely be
started by a motor no larger than is necessary to drive it, and no
excessive current is called for. There is, of course, the advantage also
that the stone can be driven at the best peripheral speed irrespective
of its diameter.

The above arrangements have been described at some length and
illustrated, not entirely on account of any merit which they possess, but
because the solution of every such problem is a help in the solution of
other problems, and many difficulties in the electric driving of machine
shops have still to be met and overcome.

It maybe remembered that a small flywheel on the motor shaft, and
a few series turns on the field, are frequently a great help in dealing
with a load such as a planing machine.

Returning now very briefly to the three cases of which particulars
have been given, and planning out the installations on the lines
which have been sketched, we shall see that very appreciable savings
can be effected, and all the advantages due to the electric drive
secured.

978

CHATWOOD: ELECTRIC DRIVING [May 7th,

1... y i f i

Scale, orft€T

Fig. 6. — Portable Electric Grinder, for dressing seams and rows of rivets in
plate-worki Motor on floor driving wheel by twisted leather belt inside tubes.

Fig. 7.— Portable Electric Grinder— Details of Head.

1903.]

IN MACHINE SHOPS.

979

Case I.

This case does not lend itself very well to much grouping, thos>e
which appear to be advisable being a small group on the lower floor
and one on the upper. These would consist of five tools each. The
installation would then require fourteen motors ranging in size from
li to 7i H.P., and averaging 2*8 H.P.

The cost of running, based on the same period as that already
given, would be —

£ s. d.

lo per cent, on installation 34 o o

Cleaning 7 10 o

Brushes 600

Current ... • 44 3 10

^91 13 10

as compared with ;£i86 7s. 2d. with the single-motor arrangement.

Fig. 8.— All Shafting shown solid.

Case II.

In this case individual speed control can be obtained in every case
where it is of very great value, and all awkward drives avoided without
the use of a large number of motors ; at the same time the dead load can
be reduced to the equivalent of 3'i H.P.

s. d.

0 0

7 8

980 CHATWOOD: ELECTRIC DRIVING [May 7th,

The number of motors would in this case be eighteen, ranging from
i\ to 6 H.P., the grouping being indicated in the table on page 969.

The cost of the installation would be £700, and the running costs on
the basis previously taken.

10 per cent, on installation

Cleaning and brushes

Current

;£i9i 7 8
as compared with ;£264 12s. 6d. with the single motor.

Case III.

By dividing the shaft in the upper shop into two, and adding
separate motors for the planing machine and the principal lathe in the
lower shop, the average dead load could be reduced to i*86 H.P.

The current consumption per 53 hours would be reduced from 174
to 85 units, of which i6'5 per cent, would be usefully employed.

The running costs for the year would now become —

£ s. d.

10 per cent, on installation ... * 19 4 o

Current 29 3 4

£A:^ 7 4

as compared with ;£68 os. lod.

It is not at all an easy matter to institute any general comparison
between the costs of steam and electric driving, but it is possible to
suggest certain approximate formulae which may be of use in arriving
at a rough approximation.

The cost of steam driving depends chiefly on the size of the plant
and on the ratio which the mean load bears to the maximum, and may
be expressed by —

A + B/» + Cr,

where ABC are constants expressed in £ per annum ;
f is the maximum I. H.P. of the engines ;
r is the mean I. H.P. taken over the year.
A represents wages in looking after boilers, engines, shafting,

and belts.
B is interest, depreciation, rent, repairs.
C is coal, oil, and stores.

1903.] IN MACHINE SHOPS. 981

The following values have been obtained in a few cases : —

o -oi
tJ1J> o

too 200 zoo AOO

Fig. 9. — Annual Cost of Steam Power. Value of Constants.

In an engineering shop of reasonable size, it is to be remembered
that the maximum load is always large compared with the mean.

Taking the case of an engine of 125 I.H.P., we get from the formula
and the "constant" curves already given the following curve giving the
relation between the ratio maximum mean load and the annual cost.

£600

rinXofpo

Fig. 10.

CHATWOOD: ELECTRIC DRIVING

[May Tth,

The cost of motor driving may be given by a formula of the same
form as that for steam driving —

A' n + B' f + a /,

where —

A' is cost of wages in attending to motors, shafting, and belts

per motor.
n is number of motors.
B' is interest, depreciation, repairs.
p' is total B.H.P. of motors installed.
C is annual cost of one B.H.P. in £,
C is given by —

where e represents the efficiency of the cables and motors as a fraction
of unity ;
X the cost of current in pence per unit ;
r' the total mean load taken over the year.
The constants in the above expression are given for a few cases by
the following curves : —

3o -9

t60

J»/ERAQ£SIZE

OFMOTORSBHRP ^ '^ ''S SO

Fig. II. — Annual Cost of Motor Distribution. Value of Constants.

Taking now a case for comparison and letting the data be as follows: —

p = 125.

r= 50

n = 25

^' = 100

giving C 11-28,

X = id.

we get / i8*3 by equating the steam and electric costs, which shows us
that under the assumed conditions if the mean useful load, together
with the average load of such shafting as may be used for grouping, is
less than 18*3 H.P., the electric is cheaper than the steam drive.

1903.] IN MACHINE SHOPS. 983

The formulae given above are not intended to be anything more
than suggestions on which each engineer may build similar formulae by
the substitution of constants suitable to the conditions which prevail
in the district and in the class of work with which he may be con-
nected.

It would be outside the scope of the present paper, which is intended
to deal rather with the use of electricity, to enter into the question of
its economical generation ; but the author would like, before closing, to
express the opinion that, unless the saving to be gained by generation
on the premises is considerable, it is wiser to procure current from an
outside source and so take advantage of the reserve plant of a central
station, and at the same time be entirely free to devote one's attention
to one's own particular business rather than for the sake of a small
apparent saving enter into the business of electrical supply with its
responsibilities and troubles.

If, however, current is generated on the premises, it must not be
forgotten that the use of batteries may, owing to the large fluctuations
of load, be productive of considerable economy.

In conclusion, the author would point out that the subject on which
he has been speaking is a very wide one, and one bristling with diffi-
culties owing to the limited amount of experimental work which is avail-
able, and that therefore he can only hope that the paper will be useful
rather as a collection of suggestions than as anything more ambitious,
and that it may in some small degree help to the intelligent apprecia-
tion of the problems involved in the application of motors to machine
shop driving.

The President : The Council thought that it might be desirable to
have the two papers read at the same meeting, so that the discussion
might be had on the two papers together. Of course at this late hour
it would be quite unreasonable to start a discussion on these valuable
papers, and therefore, I presume, we will adjourn the discussion to the
the next meeting.

The President announced that the scrutineers reported the follow-
ing candidates to have been duly elected : —

Members,
Frederick Giffard Cole. | Dr. George Finzi.

Associate Members,
Chas. Frederick Butler. I Robert Walter Grubb.

Harold Edward Donnithorne. I John Hay ward Home.
H. P. Prior.

Associates,
John Norman Alty. | Edmund Davidson.

Gwylim Anwyl Hughes.

Students.
Walter Charles Lambourn. | Wm. Stanley Lonsdale.
Donald Grant Tyrie,

984 TRANSFERS, DONATIONS TO LIBRARY, ETC. [May 14th,

The Three Hundred and Ninety-fifth Ordinary General
Meeting of the Institution was held at the Society of
Arts, Adelphi, on Thursday evening, May 14th, 1903 —
Mr. R. K. Gray, President, in the chair.

The minutes of the Ordinary General Meeting of May 7th, 1903,
were, by permission of the meeting, taken as read, and sigu^ by the
President.

The names of new candidates for election into the Institution were
taken as read, and it was ordered that they should be suspended in the
Library.

The following list of transfers was published as having been
approved by the Council: —

From the class of Associate Members to that of Members —
Gerald Henry John Hooghwinkel.

From the class of Foreign Members to that of Members —
Guido Semenza.

From the class of Students to that of Associates —

James Hally Brown. | John Blundell Butler.

Frank Knight Jewson.

Messrs. I. W. Chubb and J. Fiddes-Brown were appointed
scrutineers of the ballot for the election of new members.

Donations to the Library were announced as having been received
since the last meeting from the Astronomer Royal, Messrs. A. H.
Jackson, H. M. Leaf, and the Maschinenfabrik Oerlikon ; and to the
Building Fund from Messrs. S. V. Clirehugh, W. J. Cooper, and
W. McGeoch, to all of whom the thanks of the meeting were duly
accorded.

The President : Before beginning the discussion, I have to
announce that the Council this afternoon, believing that it would meet
with the general approval of the members of the Institution, have
decided that the Annual General Meeting should take place at the new
offices. We thought this arrangement would give an opportunity to
the members to see the new offices, which will be found spacious and
commodious : it was also thought that the convenience of members
would be better met if the hour were changed from 8 p.m., which is
the usual time of our General Meetings, to 5 o'clock in the afternoon.
You are aware that we are debarred from having any technical paper
read at those meetings, and it appeared to be superfluous and to cause
unnecessary inconvenience to bring people together in the evening at
8 o'clock to hear read the Annual Report of your Council, which

1903.] WILLIAMSON AND CHATWOOD : DISCUSSION. 986

contains matter of which to a great extent the members are already
aware.

I have no doubt, gentlemen, you will confirm the Council's
decision.

Resumption of Discussion on Papers by Mr. A. D. Williamson,
ON *' Applications of Electricity in Engineering and Ship-
building Works," and Mr. A. B. Chatwood, B.Sc, on " Electric
Driving in Machine Shops."

Mr. H. A. Mavor : I am glad to have an opportunity of expressing Mr. Mavor.
my thanks to Mr. Williamson for this paper. It |is one of the most
useful and practical papers that we have had before us, and one
that lends itself to useful discussion. There are some points, in it
which, with your permission, I would like to emphasise. We have
on page 930 an interesting table of Works Costs. I have taken the
opportunity to compare these costs, not with those of other electric
installations, but with an entirely different group of costs.

It has always seemed to me important in considering the costs of elec-
trical production, more especially in factories, that we ought to place our-
selves, not only on all fours with what we and our friends in the same
business have been able to do, but with what is being done in other
regions. I happen to have a pretty complete tabulated record (Table L) of
a group of costs taken from different parts of the country and over widely
different industries ; and I have found it interesting to compare these
costs with one another. For the sake of convenience I have reduced them
to terms of cost per unit, by translating the indicated horse-power into
units by taking 600 watts per LH.P. ; and also for convenience I have
translated the coal into a uniform price of icod. per ton, which is a
convenient figure for calculating, and not very far from about the
average cost over the country. That iworks out to o'045d. per lb.
Having the figures in that form, it is easy to see how many pounds of
coal are being used per killowatt or per horse-power as the case may be.
I find that the best kind of business for economical power production is
to be found in weaving and spinning factories. Flour mills are nearly
as good ; and the very worst and the most expensive power production
in the whole range of British industry that I have been able to find is
in engineering workshops. That is not difficult to explain, and it is
interesting in this connection, because we are here dealing with an
engineering workshop. It is pleasing to find that in this workshop the
costs of power production are not hopelessly bad ; but they are a good
deal worse than the best, and that is the point that I wish to call
attention to. I have eliminated from the comparison the repairs and
the cost of water, because they may vary under widely differing
conditions ; and as the depreciation figures in this paper are not given
in detail, I think that it would be well also to eliminate them. I have
made a very simple comparison between the best record I have of power
cost — it was a spinning mill in Lancashire — and the two first cases
which are given in some detail on pp. 930 and 931 of Mr. Williamson's
paper. The most startling difference is in the wages per unit. This is

986

WILLIAMSON AND CHATWOOD :

[May 14th,

Mr. Mavor.

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Class of Factory.

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Electrical Engineering
Chemical

1903.] APPLICATIONS OF ELECTRICITY : DISCUSSION. 987

a point which I think deserves our most careful consideration. We Mr. Mavor.
are quite accustomed to trust our lives in trains running at sixty miles
an hour, with a man of the working class and a stoker looking after the
engine, which may be of a thousand horse-power. I think you will find
it not a very difficult calculation to ascertain how much that runs out
per horse-power per hour. It is not much ; it is not anything like a
tenth of a penny per unit. The best record that I have been able to get of
actual results from year's end to year's end in wages is the equivalent of
o'022d. per unit in a spinning mill which also has a very low consump-
tion of coal. To-day I took the opportunity of going through the valuable
tables in Lightning for power productions. I am very much surprised
to find that one of the cheapest power-stations is in London — West-
minster, which is 0'i6d. per unit, Bradford and Edinburgh being each
0*09 per unit. Each of these latter is four times as high as it is in the
spinning mill. Those of us who are familiar with the conditions of
working in such factories, where power is a very important element
in the prime cost, and where consequently it has been carefully sought
to reduce it to its lowest figure, know that the conditions there are
very different from what they are in an electric generating-station. I
think it is time that we electrical engineers should realise that it is not
necessary to have expensive labour for looking after electric machinery.
If we do not believe it, then users of electric machinery are not likely
to be convinced that they can dispense with expensive labour. I am
glad to find that Mr. Williamson has grasped this point. I do not
offer this by way of criticism, but for the purpose of emphasising what,
among the multiplicity of other matters, he has not been able to so fully
call attention to. I think that it is this very point of labour cost which
leads Mr. Williamson to recommend large units running at slow speed.

Larger units would necessarily result in a very great difference in coal
economy. In fact there is considerable room for coal economy in the
cases under consideration as compared with the spinning mill I have
been referring to. The cost, correcting the price of coal to lood. per
ton, is o'i68 per unit at the mill, as against 0*27 in works (a), and
0*29 in works (6). I may incidentally point out here that I do not
quite understand Mr. Williamson's comparisons. He says there is a
difference of the tenth of a penny. I think that is largely due to coal
being cheaper in the second works. The actual saving appears to be
about the half of that, when the coal is reduced to a common figure for
cost.

The use of low-speed units is another important point which I
should like strongly to advocate here. Those of us who are building
dynamos know that the attention which a dynamo requires is entirely
at the commutator, and that if you have a high-speed commutator,
there is necessity for frequent adjustment and attention from the
attendant ; and that as our units increase in size, we ought, if we use
high-speed engines, to keep the commutators as small in diameter as is
consistent with proper working, and have the surface speed as low as
possible.

Then Mr. Williamson recommends an increase of voltage. It is
easy when one looks over an installation of this kind, with over

988 WILLIAMSON AND CHATWOOD : [May 14tb,

Mr. Mavor. io,ooo horsc-power, to say what a pity it was not begun on better lines;
but we must not forget that experience has to be gained, and experience
here thoroughly confirms what one would expect, namely, that higher
voltage and the three-wire system would be recommended for future
extensions, as Mr. Williamson mentions. I think one of the most
important features in the improvement produced by the use of bigger
units, is the abolition of the switchboard with all its complications.
The abolition of compound winding is a natural consequence of the
increase of size, because the percentage drop on big units is much
less than the drop on small ones. With big units there is no necessity
for any switchboard at all. Switches for heavy currents are very
ornamental and expensive ; but every one knows that the last thing
one thinks of is to switch off the heavy currents at the switchboard.
Those switches are never used, and therefore ought not to be there.
The abolition of the switchboard abolishes the switchboard attendant
and his cost. One point I would like to ask Mr. Williamson is, Can he
give us any record of the breakdowns that have taken place, and the
nature of them ? He mentions that the engines when opened out
show very Httle wear on the cylinders ; but what about the valves, and
what number of breakdowns have been recorded in the course of
working? I expect that his answer will be that they have been
extremely small. I wish to use this as an argument for reducing the
number of units ; we only have one engine on an express train ; we
have very many steamers crossing the ocean with only one engine — at
most two ; and therefore it does not seem as if there was any sense in
having five or six units in a power-station. On page 935 of his paper,
Mr. Williamson very rightly points out that the varying methods of
applying motors to machines do not in themselves result in great
differences in economy. The real point is that, after all, electricity is
only a means of distributing power, and that economy is to be got in
the generating station. The loss in shafting is frequently very high,
but 1 do not think we always remember that the interest on the cost of
the electric plant is also high. The real argument for adopting electric
drive is the possibility of introducing economical plant into the gene-
rating stations. Then with regard to the speed, weight, and price of
motors. If I may be pardoned for introducing a personal suggestion
of my own here, I think that if we want slow-speed motors, we cannot
do better than turn them outside in— put the armature outside the
magnet, and you at once get a very high speed for the wires on the
rotor of the machine — a high peripheral speed without a high rotative
speed. The difficulties of lubrication have been solved and there is not
any difficulty left. Some of the older members of the Institution
will remember that there was a machine in the very early days in which
there was a fixed internal magnet— the Elphinstone-Vincent machine ;
that is capable of development in a very satisfactory way. I had the
pleasure of showing last year at the Institution of Civil Engineers a
motor constructed on this principle, which gives exceedingly low speed
with a very small size — a one horse-power motor, at 500 revolutions,
only a foot in diameter and a foot long.
Big<?.^^ Mr. D. L. Selby Bigge : I have read this paper of Mr. WUliamson's

190S.] APPLICATIONS OF ELECTRICITY: DISCUSSION. 989

with the very greatest interest. For the past fourteen years I have Mr. Sciby
been engaged in the work upon which Mr. Williamson touches — that
is, the application of electric power to the driving of works and different
industries. I think that this paper is of the very greatest value. It is
practical and sound from beginning to end. The points that Mr.
Williamson brings forward, as he says, are facts within his own
experience, and they should carry great weight, I think, with the
members of this Institution. All the points that he brings forward
most thoroughly corroborate all the statements that other writers on
this subject have put forward ; in fact, my views so thoroughly coincide
with those of Mr. Williamson upon those points, that it is very difficult
for me to criticise what he has said. In going briefly through this
paper I find, looking at page 926 in the first instance, that Mr. Williamson
has had to deal with works which have been gradually growing, and
it has been very difficult for him froifi the outset to formulate a scheme
for the whole of those works. I have always found that it is of the very
greatest importance when considering a scheme for a works to take the
whole of the works into consideration from the outset, and as far as
possible to take all possible extensions into consideration ; and when
you have arrived at the whole of the power that the works are at the
present time using, and what they are likely to use in the future, then
total that power up. Supposing that the power amounts to 2,000 or
I, $00 horse-power, for the sake of argument, you then immediately split
up that power into certain fixed units ; and I think that the greatest
economy can be derived from the plant in which there are never more
than two units working at the same time. That to a certain extent
bears out what Mr. Mavor has just now said on the subject of large
units and in favour of having few units working; but I can fully
appreciate the great difficulty in Mr. Williamson's case that he had in
that direction. I had the pleasure of visiting Messrs. Vickers- Maxims'
works, when Mr. Vickers showed me all round the works at Sheffield,
so that I have some slight knowledge of the conditions that Mr.
Williamson had to tackle. I must say that the result has been most
satisfactory. In the case of the engine-works power-house I see that
he has alloV/ed for five sets ; it seems to me that to get the greatest
economy out of such a generating plant there are too many units, and
that it would have been better if it could have been so arranged as to
have made units larger and never to have more than two running at one
time. There are cases in which we have very large works being driven
off one unit, and then you have only the one superintendence of the
one unit to provide for. Of course you have the standby plant as well.
On page 932 Mr. Williamson states that his experience of " high-speed
vertical engines running under the severe conditions of continuous
heavy loads has been perfectly satisfactory." I can thoroughly corro-
borate that, for up to certain horse-powers I have found exactly the
same thing. But in the case of getting up into very large horse-powers,
such as 1,000 horse-power, 1,500 horse-power and upwards, we then
have found the greatest economy resulting from either triple expansion
engines and generators running at slow speed, or the compound hori-
zontal flywheel tvpe engines and generators, with condensing arrange-
Vol. 82. ' 66

990 WILLIAMSON AND CHATWOOD : [May 14th,

Mr. seiby ments and superheated steam up to a moderate number of degrees, to
B*g««. jjfy ^i^Q steam thoroughly, with 21II accessories such as Green s econo-

misers, water-cooling towers, and appliances of that kind. I next come
to the question of cables, which is referred to on page 932, and I notice
that a light insulation is used to avoid short circuits. That may be very
useful. Of course you have to take every case on its own merits, but
after a certain number of years the light insulation generally wears o£F,
and then you have no insulation at all. I prefer as a rule to keep
the conductors as far as possible bare. Coming to the motors, Mr.
Williamson says, " It must be owned that most of the success of electric
driving has been due to the great improvements which have recently
been made in manufacturing motors." That undoubtedly is a very
great point. The construction of motors in recent years has advanced
enormously, and breakdowns are almost unknown now with well-
constructed, carefully made, motors. "At the outset a strong effort
was made to cut down the number of sizes of motors." That is another
point which I think is very important also in works, that you should
have as few numbers of sizes of motors as possible, so that one set of
spares will do for the whole of them. On the question of gear, Mr.
Williamson says, " Friction gear is inefficient and cannot be applied for
large powers." I quite agree with. that. Also he says, " Belting is of
course applicable to nearly all cases, the slipping being a positive
advantage where heavy shocks and reversals of machines take place."
I can thoroughly corroborate that. On the question of variable-speed
motors Mr. Williamson gives some very interesting particulars, and the
case he tells us of a 5 horse-power motor with a range of from 300 to
900 revolutions for the return stroke, running at the high speed of the
motor, is very interesting in the case of a lathe or planer. I notice
that Mr. Williamson states that there are about no variable-speed
motors in use at the Sheffield works, showing that they have found
those to be a distinct advantage. The rest of the paper deals very
largely with motor tests, and will be no doubt very valuable indeed as
a reference. On page 954 Mr. Williamson gives us the specific case of
the Wellman charger, which shows the very great economy that can be
derived from the appUcation of electric driving. He says, *' Summing
up the advantages, we have a reduction in the wage costs of melting of
50 per cent., with an increase in the output of 25 per cent." That is
very strong evidence in favour of such machinery. On page 962 Mr.
Williamson says, " It would be interesting to hear some experiences of
engineers with circuit-breakers fitted in such power installations as
those described in this paper." If I may be allowed to give ray own
personal experience in the matter, it is this, that we find that for small
machines and small tools, such as punches, shears, and such like
machinery, the circuit-breaker is in most cases a nuisance rather than
a benefit, and we find it best in such a case to apply distributing
switchboards fitted up with fuses to the different motors. We find that
to be the most practical and sound practice. The next point which
Mr. W'illiamson deals with (on the same page) is the saving due to
electric driving. It is very difficult indeed to arrive at the saving due
to electric driving unless you have absolutely parallel cases— that is.

1903.] APPLICATIONS OF ELECTRICITY: DISCUSSION. 991

unless you take a works that was formerly driven by steam and Mr.Seiby .

completely equip it with electric power, and then compare the results ®*****

after the transformation with the actual work done before. That i3

the only way to get at an accurate result. Some time ago I spent a

very great deal of time and attention on that very point, and I tried to

get a number of statistics. I found that in the majority of instances

the saving due to the introduction of electric driving in place of steam

(that is to say, in works such as shipyards, or works where the power

was subdivided up into a very large number of units) varied between

35 and 50 per cent. That was drawn not from one case, but from a

great number of different works. I got the opinions of the different

works' owners and managers on that very point, asking them what they

had found was the actual saving after the substitution of electric driving

for steam. It varied, as I say, between 35 and 50 per cent. I see that

Mr. Williamson has done even better than that, because hQ states that

at their works the actual result was the saving of half the coal bill, with

an increase of over 50 per cent, in the output.

Dr. B. WiESENGRUND : It would be interesting to learn from Mr. 2lindf****°
Williamson whether, at least for the plants erected in 1897 and later,
alternating current has not been considered ; or what have been the
reasons for adopting 220-volt continuous-current plants even for the
latest installations. Considering the large extent of the works, it would
seem likely that alternating current would have offered advantages in
first cost as well as in maintenance. Perhaps the question of speed
regulation gave the decision in favour of continuous current. It may
be of some interest that the difficulty of speed regulation with alter-
nating-current motors is overcome in an arrangement patented by Mr.
Wiist, Zurich, who uses different stators and rotors with different
numbers of poles combined in a common casing. The outputs of the
different elements need not be necessarily equal ; it is possible to
arrange, for instance, the maximum output at the lowest speed. These
motors, together with suitable gearing arrangements, give exceedingly
simple designs of electric machine tools which I might differentiate
from those originally designed for other kinds of drives. For the
complete success of electric power transmission in engineering work»
it seems necessary that machine tool manufacturers and electrical
engineers should work in unison, and probably this union would bring
to the front designs similar in simplicity to those of which I would have
pleasure in putting before you some drawings and photo prints. In
these designs the motor is a component part of the machines, and its
attachment to the working portion, avoiding intermediate gearing,
produces a considerable saving in power and first cost of the machines,
besides the latter being much more compact than the ordinary designs.
The apphcation of a continuous-current motor with speed regulation
described by Mr. Williamson in a vertical planer or slotting machine,
the motor reversing at each stroke of the machine, is certainly very
interesting, but it can only be regarded as an example of the hard work
that modem motors can stand. Whether such an arrangement is
advisable from a technical point of view seems doubtful. The special
conditions in planing machines, namely, slow working and quick

992 WILLIAMSON AND CHATWOOD : [May 14th,

Dr. wicscii- return stroke, make it desirable not to reverse the direction of rotation
^™°'*' "' of the motor, but to make use of the kinetic energy accumulated during
the working stroke in the motor or a flywheel for the quick return
stroke, and only to raise the speed of the motor together with the
reversal of the machine. An arrangement similar to that adopted in
a hoisting drum, namely, two bevel wheels always engaging with the
driving wheel on the motor shaft, the wheels being operated by a
friction clutch, the coupling to the machine formed as a fl)rwheel
would answer the purposes. With a multi -speed Wiist motor it is
very simple to change direction of motion of the gear and motor
element in circuit by means of one lever automatically. In such a
case a short-circuited rotor can be used, as the motor can be started in
the central position of the clutch without load. It would be interesting
to learn whether any experiments have been made in this country to
regulate the speed of continuous-current motors by means of altering
the depth of the air-gap. Mr. Wiist has designed, patented, and
successfully applied this principle to many motors with two, four, and
more poles, always operating with a single lever. With regard to the
gearing, it would be interesting to hear whether any experiments have
been made at Messrs. Vickers, Son & Maxim's with double helical
wheels. The advantage of such wheels is the entire absence of back-
lash, ensuring noiseless running, especially if the wheels are machine-
cut out of the solid, as patented and manufactured by Messrs. Wust
and Co., Seebach-Ziirich. As double reduction gears, in a special
arrangement made as a substitute for worm gears, for reductions
up to 1 : 60 a minimum efficiency of 90 per cent, can be guaranteed.
Mr. AUen. Mr. W. H. Allen : In reference to the driving arrangements

shown on page 935 of Mr. Williamson's paper, nothing is said with
reference to the resistance which is given in the matter of shafting.
When we designed the works at Bedford I thought that we might
bring about economies in some directions by improvements in the
mechanical movement, so I sent round to a large number of works in
this country and in America to compare notes how they distributed the
resistance from the generating power independent of the drive, that is
whether it was mechanical or electric. We found that the average was
something as follows : one-half of the power was expended in the
shafting, the other half was expended in the movement of the tool and
the work done. No tool maker has yet made any determination to try
and improve the efficiency of the tools, and it is lamentable to see what
a large amount of effort is taken in actually working the tool, while so
very little is taken in the actual work done of cutting the metal. The
best and largest tools only give us a duty of about 30 per cent, of the
total generating power, while in the case of the smaller tools they give
us as low as 10 or 15 per cent. Nothing much can be done, however,
in the economy of these two divisions of the generating power ; but in
the matter of the shafting we have been enabled to show a very
considerable saving by dispensing entirely with the top gearing. The
power taken for driving the shaft may be divided as follows : it is
50 per cent, for the whole shaft, 25 per cent, being for the shafting pure
and simple, while the top gearing absorbs the other 25 per <?^nt. If the

1908.] APPLICATIONS OF ELECTRICITY: DISCUSSION. 998

latter can be dispensed with, we have a wholesale saving of 25 per Mr. ^if n. y
cent, of the total generating power. At Bedford we made an effort to
save that, with very considerable success, by eliminating top gearing
and substituting a cone or sleeve on the shafting itself, which was
worked by a cone clutch. It may surprise those who have never gone
into it, to learn that of the whole number of tools at work in an
engineer's shop, nearly half are idle all the day long ; only 50 per cent.
of the tools are actually at work at the various processes which they
have to perform. When tools are idle, under the old mechanical form
of drive, you have to work the top gearing and the belting at a loss of
25 per cent., whereas at Bedford, by the means we have employed
there of using the cone, the moment the machine is out of gear the
whole of its resistance is saved against the generator. I hold that to
be a very considerable saving. It has been adopted by several other
gentlemen who have built works since we started. There is one other
advantage in the employment of this particular form — that is, that each
tool can be driven separately by an individual motor in case of
emergency, as for overtime or in the dinner-time. We have a small
barrow in which there is a motor which is wheeled up to any particular
tool, and in a few minutes that tool is at work independently of the
main generating plant. As I have said, the saving derived from the
method we have employed at Bedford is as much as 25 per cent of the
whole of the generating power from the main engine. I think that is
worth knowing in designing works of this description.

Mr. J. S. Fairfax: Mr. Williamson, in his most excellent paper, Mr. Fairfax
says that 1,311 motors have been applied to driving eleven different
classes of works in seven different districts or workshops throughout
the country. It seems to me that the experience which he gives us
will be of the utmost importance and advantage to both mechanical
and electrical engineers. He states also his experience of the gearing
that he has employed. He has used seven different kinds of drive,
but the only three which he feels are to be depended upon are spur
gearing, belting, and chain gearing. So far, the machine tool makers
have designed their machines from the line shafting, and therefore
when you apply electric motors to the driving of these tools there is a
great difference in the speed, which must, of course, be reduced by
outside gearing. Mr. Williamson seems to have endeavoured to
standardise his speeds as well as the dimensions of his motors, for it
appears that the majority of them (although, of course, there is a great
deal of discrepancy according to the work) were run at about 600
revolutions per minute. The electric motor builders do not seem to
have met that problem as much as they might have done. They might
have used some mechanical means for reducing their speed to a speed
somewhat approaching that of a line shaft, as the full motor speed is
seldom required. Mr. Williamson has used his variable-speed motor,
and found it a very great success. Certainly it is an advantage to use
it for many reciprocating tools, and also for drills and boring machines,
and tools of that sort I think his motor is capable of very large
development in the future. Incidentally it is readily used to measure
the power given to each tool under different conditions of working,

'994

WILLIAMSON AND CHATWOOD :

[May 14th,

Mr. Fairfax, and may thus bring about a great saving of power, as suggested by Mr.
Allen. I have been giving some little attention to this matter of motor
driving, and I would apply the gearing directly on the motor — whether
it is an engine or an electric motor makes no difference ; and instead
of doing it in the usual way by reducing the speed outside the motor,
I would make the motor pulley — supposing it is driving a belt — ^go
round a fewer number of revolutions than the armature shaft. The
model that is here is part of the motor itself^ and gives a reduction of
about 17 or 18 per cent., but the principle is capable of going up to
about 35 or 40 per cent, reduction, so that in a case where you are
using motors that have an armature sp>eed of 600 revolutions a minute,
the arrangement shown by the model would give, say, 400 revolutions
a minute at the pulley. Then, if you were to put in a second pulley,
as there is in the model, you could get a variation of speed. By
turning the little steel shaft round there, you will see that the model
shows three different speeds. There is a variation of about ij per
cent, between those two pulleys, but you can make the variation much
greater than that. If you put on an outside bearing, you can have four
pulleys, and suppose the armatiM*e shaft is running at 1,000 revolutions,
you can reduce down one pulley to 800, the next to 750, the next to 700,
and the fourth to 650. You will notice the peculiarity that, although
all the pulleys are of the same diameter, they give four different speeds,
so that you can drive on to a drum on a lathe, dispensing with cone
pulleys, and change your speed while the machine is running, so that
you have not to stop the machine at all. You can do that from each
end of the armatiu-e shaft. If you want the greatest reduction possible,
without variation, you simply put on one pulley and make your full
reduction on that. There is another arrangement by which speed can
be reduced from perhaps 5 or 10 to one. The great point is that it
can be put on any motor and be self-contained without any outside
bearing whatever, so that the motor can be hung up on a ceiling, or
fastened immediately to the wall, ready to drive a machine.

Mr. Barker. Mr. J. H. Barkbr : I would like to controvert Mr. Mavor's remarks

about the locomotive. He says a locomotive on a main line is run
with no standby. Although the locomotive is reputed to be so reliable
as to need no duplicate, yet if it is worked out, we find that the run
per engine is only about fifty miles a day ; the rest of their time is
spent in the repairing shop. As a manufacturer, I should be very
sorry to trust to a single locomotive in my power-house.

Mr. Russell. Mr. S. A. RussELL : I have read this paper with very great pleasure
on account of the great number of facts which it lays before us. The
paper is indeed so full of facts that it lends itself very little to criticism.
I think that, perhaps, the best way of taking part in the discussion will
be to give a few notes of my own experience of motor-driving at the
Silvertown factory of the India Rubber Company. The whole factory
is not driven electrically, as we have many good economical engines
driving through small amounts of shafting, and it was decided that it
would not serve any useful purpose to replace those engines by electric
drive. We had, however, plenty of engines a good deal older which
were not very economical, being supplied through long ranges of steam

1903.] APPLICATIONS OF ELECTRICITY: DISCUSSION. 996

piping or transmitting their power through a great deal of shafting. Mr. RosmU.
We commenced by replacing those, and also by fitting electric drive to
all extensions and new work. In that way we have arrived at a total
of over 150 motors aggregating about 3,500 H.P., and varying in size
from 150 H.P. down to i H.P. The class of work done is very various
and is of a very intermittent character, and many of the machines at *
one part of the operation take several times as much power as the
average. Our 3,500 H.P. of motors does not call for more than a
maximum of 1,200 k.w. from the generating station, and the average
output taken over all the hours of running is only about 300 k.w. That
is partly due to the reasons just named, and partly also because we
have to run at night for a very small load. I am sorry to say we
cannot show such good results in the cost of generation as those that
Mr. Williamson gives in his paper for the Sheffield Works. At the
present time our plant is not working condensing, but we hope that it
will be so shortly ; and that, coupled with the low load-factor, makes
our costs more like those obtained at Erith and Barrow than those very
excellent ones which were obtained at Sheffield. As to the class of
work that we do with electric drive, we use it for tools such as lathes,
planers, drillers, and wood-working machinery ; for machines for
making rubber and guttapercha where we get very varying and heavy
loads, for cable-making machinery, and for a number of general
purposes, such as driving stamping presses, pumps, air presses, lifts,
cranes, pile drivers, capstans, and fans. With regard to the question
of separate motors for each machine or group of machines, we have
made a general rule that any machine requiring more than 5 H.P.
should have a separate motor, but we depart from this in various cases.
For instance, we have a line of similar machines driven from a line
shaft, and there we find it better not to drive all by one motor, nor to
put a motor to each machine, but to divide the big group up into two or
more smaller groups each with its own motor, arranged so that practically
any number of machines can be used according to the requirements
without ever having any appreciable amount of idle shafting or
machinery running. Also we have found it advisable with machines
such as stamping presses, punches, and planers, where there is a con-
siderable variation in the load during a cycle of the operation, to group
two Or three together on a motor if it can be done without loss through
a great deal of idle machinery running, the object being to save having
to put heavy flywheels on the motors to overcome the variation of the
load. We have also a number of motors smaller than 5 H.P., but we
have avoided those as much as possible. It is necessary sometimes,
owing to the position of a machine in the shop, or owing to the nature
of the work, to use smaller motors, but I think that the extra capital
cost and the lower efficiency, and, in the case of very small motors, the
extra cost of .maintenance, all tend to make it uneconomical to use
motors of much less than 5 H.P. We therefore avoid them when
possible. With regard to gearing, Mr. Williamson has named spur-
gearing, chain-gearing, and belting as the only three gears which have
given satisfactory results. We use all three of those, but we also use
a great deal of worm-gearing, not for small loads or intermittent work,

996 WILLIAMSON AND CHATWOOD : [May 14Ui,

Mr. Runeii. but for driving slow-running machinery which in some cases takes up
to 150 H.P. per machine. The machines are used in the manufacture
of rubber, and they have a very heavy and varying load. We have
found that worm-gearing has given us very sati^actory results. It is
impossible to make accurate measurements of efficiency with a load
varying in that way, but in comparing machines driven through worm-
gearing and machines driven through a train of spur-wheels, we cannot
find any very appreciable difference in the amount of power taken
by the motors. I do not think the loss is anything like so considerable
as many people suppose, if the worm-gearing is well made. I might
mention that we are not using ball thrusts, but a thrust block something
like an ordinary marine block ; but the collars on the shaft, instead of
being part of the solid forging, are separate collars threaded on feathers
with distance pieces in between. These have been made separately,
because we can more easily harden them and get a much better surface,
and that makes an enormous difference in the friction losses. The
rings in the block are phosphor-bronze rings, and between the collars
and the rings are two loose rings, one of phosphor-bronze and one of
steel, to reduce the surface speed of the rubbing parts. We have had
these thrust blocks and worm-gearing in use for over two years, and the
wear on the worm and thrust is quite inappreciable. They take up
much less room than a train of spur-wheels, and they run much more
smoothly and silently under a varying load. The cost of the worm-gear
at various places where we have compared alternative schemes seems
to run about 15 per cent, higher than the cost of spur-gear. With
regard to chain-gear we have not had much experience, as we have
only a few drives with it, but we find it most useful where two shafts
cannot be put far enough apart for a belt drive, nor close enough for
spur-gearing. We find the chain-gearing is from 25 to 50 per cent
dearer than spur-gearing, and I should be glad to hear from Mr.
Williamson whether he finds that there is that difference in his
experience. Another matter which is referred to in the paper is the
type of motor and the improvements made in recent years. All our
recent motors are of course multi-polar with slotted cores, but we have
a large number of smooth-core motors, both bi-polar and multi-polar,
which have been in work for a number of years. There is no doubt
that the small wire-wound armature with the smooth core is very
inferior to the former-wound slotted-core armature. With the smooth-
core machines with drum-bar armatures we have got very excellent
results, and we have had motors which stand very severe work. We
have several of 75 H.P. with smooth cores, which have been running
for Hvc or six years driving rubber machinery, where the load frequently
varies from absolutely light load (that is, merely driving the machine
round) to 25 or 50 per cent, over full load as tlie rubber enters and
leaves the rolls. I am pleased to say that during all this time we have
not had a breakdown of an armature on one of these machines. I
think that shows that the smooth-core machine is really capable of
doing a great deal more than many people credit it witli. I should put
the change from copper to carbon brushes as almost a more important
change in allowing us to deal with motor drives as we do now. About

1903] APPLICATIONS OF ELECTRICITY: DISCUSSION. 997

circuit breakers, we have tried circuit breakers in the circuit of our Mr. RusaeU.
motors, but have had to give them up and to revert to fuses, as we find
that they are very uncertain. In the shops, of course, they are exposed
to a certain amount of dust and a certain amount of damp, and we were
continually finding that the circuit breakers stuck.

Mr. E. KiLBURN Scott : One thing which should be borne in mind Mr. KUbum
in applying electric motors to a shop which has already been driven by ^°*^'
shafting is the flywheel capacity of the motor. In making a motor we
always try to get the armature and moving parts as small as possible ;
but if you put a motor to drive machinery which has already been
actuated by line shafting, having a large number of pullies and belts
and so on, you have there a good deal of flywheel power, and there-
fore, in applying motors to such machinery, it is well to provide
flywheels on the motor shafts or else in the gearing. It might pay to
reconstruct the motor, and as I suggested some time ago, build the
armatures very large indeed — in fact build the armature outside the
field so as to get increased diameter and weight.

In one of the largest railway works in this country I recently noticed
an overhead travelling crane which is somewhat novel. The travelling
and traversing motions were driven by means of electric motors in the
usual way, but in this particular case the heavy lift was effected by a
pump and hydraulic mechanism on th^ crab. The pump was driven
by electric power, and a very nice exact lift was obtained by means of
the hydraulic ram, which, I believe, would not have been possible if the
electric motor hacf been coupled-up direct.

The authors of both these papers have dealt only with continuous-
current motors, but I do feel that in this motor work we are coming to
driving by three-phase. From a purely manufacturing point of view,
one finds that in plants fitted with three-phase motors there is never
any trouble about breakdowns or difliculty with the starting gear. But
with the continuous-current motors you may have a breakdown if the
" no load " or " overload " release gets out of order, or, as sometimes
happens, they are tied up to prevent them acting. It is the nature of
the continuous-current motor to be coddled in this way, and, moreover,
even if there is no sparking an attendant must go round regularly to fit
new brushes. With a three-phase motor, having a short-circuited rotor,
such as are used for driving a good many modern workshops, there are
no brushes, and the starting switch is of the simplest kind with nothing
to get out of order or be tied up. Again, more often than not motors
get into dusty places, and a cover must be provided to protect the
commutator, or the motor may have to be entirely enclosed and its
output considerably reduced. Now I believe the enclosed motor is
distinctly a fad, and it is very seldom, if ever, necessary with the much
simpler three-phase motor.

Another point in connection with three-phase is that the motor
speed depends primarily on the periodicity. And as most machines
require a steady speed, the three-phase motor is thus very desirable.
This feature is particularly useful when driving textile machinery, as is
proved by the extensive adoption of the three-phase motor in textile
factories abroad. It is often urged against the three-phase motor that

998 WILLIAMSON AND CHATWOOD : [May 14th.

Mr. KUburn you Cannot get a variable speed with it, but such variation is easily
attainable. For small variations resistances can be used, and for large
variatioiis the cascade system or varying the number of stator-poles
may be employed. As a matter of fact the long taper cone pulleys
with a short belt between gives a very easy and cheap method of
varying speed for large lathes, etc. I do not think, therefore, that you
can bring the objection against the three-phase motor that you cannot
get variable speeds, because if need be you can get large changes
by altering the stator-poles, and you can get small intermediate changes
by a puir of taper cone pulleys. Another point is that if you go to the
trouble of measuring up the space occupied by a three-phase motor as
compared with a continuous-current motor, you will find that if you are
limited to space, you will get your three-phase motor in all right where
you will not get the continuous-current motor ; that follows from the
construction of the two machines. Whatever may be case just now. the
three-phase motor is bound to come out cheaper in the end, as it is so
much easier and cheaper to make.

It may be mentioned that there is very much greater uniformity in
the speeds of three-phase motors : thus at 50 periods per second no
synchronous speed is possible between 600 and 750 or between 750 and
1,000, and whatever the make of motor the speed will be these figures
less the slip of 3 or 5 per cent, as the caSe may be. Without effort or
trouble therefore the speeds of three-phase motors have become
standardised, and this is a very real convenience wjien appl3ring such
motors to machines.

Mr.Gaster. Mr. L. Gaster : I can also corroborate the great advantages of

applying electric driving in works. Allusion has been made to the
use of the polyphase motor for driving in factories, and whilst not
wishing to discuss at this juncture the merits of the polyphase versus
direct current, I should like to mention a case which came under my
notice during my visit to Roumania last year. I had the opportunity of
seeing there the application on a very large scale of the polyphase
motor used for boring the wells in the petroleum oil fields, for pumping
the oil, and for driving all the tools in the workshop of the Company.
The power is generated from a waterfall available about 25 miles away
from the oil fields, and the fact that the water-power is cheaply trans-
mitted and that the motors are sparkless when using the polyphase
current, led the Company to adopt the polyphase in preference to the
direct-current system. The Company is effecting great economies in
using electric motors instead of the great number of scattered boilers and
engines employed previously, which not only were more costly to run,
but also more dangerous on account of the fire risks. The application
of electric motors to the boring of wells is extending rapidly also in the
Russian oil fields. I am often asked how it is that polyphase motors
are not so much used here ; but the reply seems to me to be simple
enough, in that there has been but little opportunity here for their
development up to a short time ago. There are, however, signs of an
inci easing demand in the near future, the reason being, that the power
will have to be transmitted at a long distance from large central
stations which are being established throughout the country. I

1903.] APPLICATIONS OK ELECTRICITY : DISCUSSION. 999

remember Professor Weber of Zurich teaching us thoroughly first as Mr. Gaster.
to alternating current, saying, that if you understand thoroughly the
alternating current, which is the originator of the direct current, it is
not so difficult to understand the latter. The progress made in the
development of the polyphase motor gives every encouragement as to
its future in this country.

I should like to ask Mr. Williamson a question with regard to the
generating plant used on the works mentioned. I notice that there is
a very great difference in the cost per unit generated. At Erith, for
instance, fuel costs 20s. per ton, and the works-costs there per unit are
about I'id. ; in Barrow, with a cost for fuel of 17s. per ton, the works-
costs per unit are about i*3d., while at the Electric and Ordnance
Accessories Company, although the fuel costs 19s. lod. per ton, they only
pay o'55d. for the biggest part of the works-costs per unit. Probably in
the latter case it is due to the use of a gas plant (Dowson), which I
notice that they have there. I see also that the present plant capacity
is only 375 kilowatts, and that the annual output is only 364,000 units.
Comparing the result of works (g) with those others where the price of
fuel is the same, but where the plant capacity is larger, and the output
ranging from 644,000 units to three and a half million units annually,
the price at the Electrical Ordnance Accessories Company compares
very favourably. I should like to know whether it would not pay in
the future to have gas-generators for driving instead of steam engines ?
because gas engines can be made now for very large units, and they
certainly have a great future before them. There is an enormous
difference in the price of fuel between the two plants (6) and (g), and
where fuel is dear, the economy produced in using gas engines is very
great, the fuel item playing a very considerable part in the generating
costs. Referring to the remark made by the author concerning the
preference of fuses versus ** overload release,*' I quite agree with him
that the use of the fuse as a protection is a much less troublesome
arrangement, but unfortunately there does not exist a sufficiently clear
understanding between the different makers of fuse and fuse-boxes to
produce one good type which could be adopted universally. I think
that it is now time that something should be done in the matter, and
that we arrive at some understanding as to the standard type to be
adopted, and so do away with the existing discrepancies.

I wish to draw special attention to the following point Some
contractors say that they will make electricity very cheaply, and they
put in the plant anyhow and say, " That it will be all right " ; but they
often omit to explain to the purchaser the proper way to treat his
motor, leaving him under the impression that the motor can do
wonders, but he soon finds out that in not having been provided with
sufficient spare plant in case of a breakdown, the whole works have
to be stopped until the repairs are done, which causes a very great
loss. In factories where the value of the goods turned out by the use
of the motor is of many times greater value than the cost of driving
the motors, a breakdown leads to very great loss to the user of the
motor. It must be pointed out that only the best class of workmanship
and the best material have to be applied, if electric driving is to be used

1000 WILLIAMSON AND CHATWOOD : [May 14th,

Mr.Gaster. successfully and economically in the long run. There are several
small trades like tailoring, cap-making, tobacco-cutting, etc., where
electric driving could be considerably used, but the people are simply
frightened away from motors on account of the troubles they some-
times give, which to my mind are mostly due to cheap and unreliable
fitting up. Contractors ought not to undertake to put up motors, or
any other electrical installation, at so cheap a rate as not to allow them
to ensure good finish. They should remember that it will greatly
assist the further development of the application of electric driving
in factories, if they will explain to the would-be customer that it is
absolutely necessary to have first-rate motors, sufficient spare plant,
and that a judicious distribution of the driving power will make his
factory more efficient. Only in this way can we safely expect a wider
extension of electric driving generally.

Patcheii. ^^' ^' ^' Patch ell: In regard to the remarks of previous

speakers in the discussion, Mr. Barker has said that locomotives only
run one hour a day, and spend the other 23 in the repairing shop. I
do not understand the figures I [Mr. Barker : I said they only ran
50 miles a day.] You can take it as one hour, because they often go
60 miles in the hour, I think that we might probably prove by figures
that the whole of the electric plant in the country could do the present
output if worked one hour a day at full load, such is the inefficiency
of the conditions under which it is worked. Then Mr. Scott votes
exclusively for three-phase motors. I do not think really that there is
a "best" for everything. Each has its best place. I have between
9,000 and 10,000 horse-power in direct current, and I have between
9,000 and 10,000 horse-power in three-phase current; but I do not
throw down my challenge and say which is the best — each has its best
place. We hear a great deal glibly talked about the variable speeds
of three-phase machinery ; but when you ask a man who is talking
like that to put his views on paper and talk about an order, he is
immediately very busy — he has to go off somewhere else very urgently,
and he cannot attend to it !

To come more directly to the paper, there is one important point
in factory driving which I should like to know more about, if Mr.
Williamson would tell us. As regards generators, they are generally
wound as shunt machines. In the paper sometimes Mr. Williamson
says "shunt" and in other cases he does not say whether they are
shunt or "compound." Station meii, in thinking of a dynamo,
generally think of it as a shunt machine, because if we are fortunate
enough to be supplying direct current, we want to put them in parallel
with the battery, and if you start doing that with a compound machine
you often get fireworks ; so we generally go in for shunt machines. [Mr.
Williamson : They are all shunt right through.] A small compound
machine will do for small works better perhaps than a shunt ; but
when you get into big works, I think that a shunt machine is the best
thing to put in. Has Mr. Williamson tried the compounding of motors ?
[Mr. Williamson : Many of them are compound.] I think that one of
the prettiest things described in the whole paper is the variable-speed
reversing motor. One has been in the habit of using heavy planing

1908.] APPLICATIONS OF ELECTRICITY: DISCUSSION. 1001

machines, taking a cut in each direction, but if they are vertical Mr.
machines there are difficulties in the way of doing that, and this is a ^*^'**"*
very beautiful instance of the way in which the electrical engineer can
come to the rescue of the manufacturer. Mr. Allen mentioned his
cones, but I do not think that he said enough in favour of them. I
was greatly struck by the use of them on small tools when I went
through the Bedford shops some six or seven years ago. They are not
only very handy, but they save in the construction of the shop, and
they also save light. You get the light down far better if you have got
no horizontal belts from the main shaft across to the counter shaft.
Mr. Russell spoke about smooth cores and slotted cores. I have tried
both. I have had smooth cores with steel teeth ; in the course of time
they chafed through — the machines I am speaking of now are probably
ten or twelve years old, and the machines of that date got rather warmer
than machines do nowadays ; that helped the cutting through, because
the expansion during load slackened up the insulation, and then when
we ran up again we got more chafing. As time went on we got
machines with wooden teeth ; they did not short-circuit on the steel
pegs, because there were no steel pegs to short-circuit on ; but if you
happened to have a short-circuit outside, you could take the teeth out
by the handful 1

Mr. R. Hammond : It is a very great pleasure to have results placed Jp*
before us in so exact a manner as they are in Mr. Williamson's paper.
It is a tempting paper, but I will just confine myself to discussing the
point of cost of production. Some years ago, on one of the earliest
Power Bills, Mr. Williamson was produced as one who could show
that electricity could be generated and distributed at under one penny
per unit, which in the dark ages of 1893 was considered a very low
price indeed. Here he shows that in the two Sheffield works he has
broughtthe costs down, in the one case, to o7i6d., and, in the other case,
to o*675d. He certainly does demonstrate a fact that is often questioned,
namely, that it is quite possible to produce and distribute electricity at
a profit at a penny per unit. With the average costs that appear in
the Journal that was referred to by Mr. Mavor of 1*5 and even 2d. per
unit, Parliamentary Committees wonder how it is that any portion of
the power can be produced at so low a figure as id. per unit ; but here
we have it in black and white, and that most satisfactorily disposes of
the idea that it is an impossibility. I should like Mr. Williamson in his
reply to tell us how it is that his coal comes out at so high a figure.
With such a magnificent load-factor I should have thought that the
coal would be less, in the case of the North Sheffield station, than
o'3i5d. per unit, and in the case of the South Sheffield statioii, than
o'255d. per unit. We are well acquainted with stations in this country
which, working on the very moderate load-factors of 10, 11, and 12 per
cent., are achieving results equal to that ; and I am curious to know, as
1 am sure we all must be, how it is that, at Sheffield, so high a propor-
tion is absorbed for coal. Possibly Mr. Williamson in his reply will be
able to give us an idea of the calorific value of the Sheffield coal. The
very high cost of po^J seems to me to be the only weak spot in the
paper.

1002

WILLIAMSON AND CHATWOOD ;

[May Uth,

Mr.
PatcheU.

Mr.

Hammond.

Dr. Rhodes.

Mr. Aitken.

Mr. W. H. Patchell : Mr. Hammond got very near it, but he did
not quite hit the buil's-eye this time. Tlie figure for coal in the paper
is per unit generated, and the coal that Mr. Hammond has in his mind
(which he has got from the Electrical Times tables) is coal per unit sold
— which is a very different thing.

Mr. Hammond : Thank you ; I am very much obliged to you for
pointing that out.

Dr. W. G. Rhodes (communicated) : One of the points naturally
arising out of Mr. Chatwood's interesting paper is the choice between
alternating- and direct-current motors for machine driving.

As the author points out, where the speed of the machinery is
required to be constantly varied between wide limits the advantage
lies with the direct-current motor, but if, as is often the case, the speed
should be kept as constant as possible, the alternating-current motor
has decided advantages. In private installations the current taken by
the motor at start is not a matter of great importance, and an induction
motor of the squirrel-cage type can now be made to rival the shunt-
wound direct-current motor both as regards efficiency and constancy
of speed, and at the same time is quite free from sparking troubles,
which constitute the great drawback of direct-current machines. Not
only is the fire risk less with induction motors, but they require less
attention and cost but little in repairs.

I must say that I differ from the author in advocating the purchase
of power from Corporations. It is quite true that the large margin of
power available is an argument in favour of this ; but where the demand
is large it is far cheaper to install a generating plant, on account of the
lower standing charges and the fact that there is then no network of
mains which have to be paid for out of revenue. It not unfrequcntly
happens, too, that a Corporation refuses to connect motors above a
given rated power, on account of their inability at certain times of
coping with such a large additional demand.

The lowest charge made, to my knowledge, by any Cor|X)ration for
energy is id. per B.O.T. unit, and this charge is only reached after a
certain minimum demand is guaranteed. If, as is frequendy the case,
there is available steam, a private installation can generate at a cost of
id. per unit ; in fact it can be done at this price including all charges
for interest, depreciation, etc., by installing a gas engine with direct-
driven generator.

The precaution of arranging that the voltage of the private instal-
lation should be the same as that of the town supply is a very wise one,
for then the latter can be counted on in an emergency.

Mr.* James Aitken {communicated) : With regard to Mr. William,-
son's choice of a voltage under 250, I agree with him that it will meet
the requirements of all ordinary-sized works. If this pressure is
exceeded, certain restrictions are imposed by the Board of Trade, and
special care has to be taken in the selection of suitable controllers for
voltages of 400 and upwards to prevent sparking. In the works I am
connected with — the class of machines are ship-yard tools — we have
adopted the individual motor drive for the machines, and, wherever
possible, have used direct spur-gear drive from the motor to the

1903.] APPLICATIONS OF ELECTRICITY: DISCUSSION. 1003

machine, the gear consisting of forged
steel pinions and steel-rimmed wheels
machine-cut. In using spur-gear care
should be used in selecting the motor,
as the ordinary motor for belt drive is
generally too light in the armature
spindle, and cau^s chattering. Until
recently it was difficult to get motors
suitable for spur-gear ; these can now
be obtained, and there is no reason why
spur-gear should not be more generally
used, and thus do away with the belt-
ing and attendant pulleys.

On page 1004 is a list of a number
of machines showing the current taken,
horse-power to drive the machine, and
horse-power doing useful work. It may
be interesting to compare these with
the list in Mr. Williamson's paper. The
tests have been taken from the machines
working under normal conditions.

It will be noticed that in many cases
the power consumed in driving the
machine empty is a very great propor-
tion of the total power used. This is
also shown in Mr. Williamson's results.
The object one should keep in view is
therefore to get your motor as close
up to the work as possible.

As an example of this, take a high-
speed radial drill running at 400 revolu-
tions per minute with }" twist drill.

Horse-power registered to drive
machine

Horse-power registered .to drive
machine running light ... 50

Horse-power doing useful work 25
This machine is direct spur-geared
in the usual way. If a variable-speed
motor be placed on the drill-spindle
saddle, and direct connected to the
drill spindle with a pair of bevel
wheels, 4 H.P. would be saved. In
the latest practice this method is being
adopted.

With regard to the fluctuation of
the load, the cranes give the most
trouble, as they take a large amount
of current for short periods. If the

Amp ere 6

Mr. Aitken.

Fig. a.

1004

WILLIAMSON AND CHATWOOD :

[May 14th,

List of Machines, with Horse-Power Required, etc.
220 Volts. (Aitken.)

T^'PK OF Machine and Work

OPFRATBD UPON.

Amperes

REQUIRED
BY

Machine.

H.P.TO
DRIVE

Machine.

H.P. I'SED 1

FOR USEFUL REMARKS.
WORK. 1

Cold Iron Circular Saw, cutting)
14" X 6" R.S.J [

Ditto, running light

I2i

3-68
148

Drive, direct spur-
connected, steel
wheels.

Drive, direct spur-
connected, stcd
wheels.

Iron Band Sawing Machine, cutting i .
solid steel Bloom 3" thick ... • ^

Ditto, running Ught , 5

2-06
148

•58

Joist Straightening Press, stralchten- [
ing 5" X 4" X 1" steel angle ... i

Ditto, straightening 16" x 6" R.S.J.

Ditto, running light

4-42
20-6

2-06

1-36 1

18-54

...

Drive, direct spur-
• connected, steel
wheels.

Large Double-ptmchlng Machine. ]
punching i" holes through j"
plate

Ditto, running light

20
18

59
530

•6

) Belt drive, very
[ heavy flywhccL

Punching and Shearing Machine,
shearing §" pUte, punching? J"
In J" plate )

Ditto, running Ught

Combined Punch Shears and Angle)
Cutter, cropping 6" x 4" x |" \
sttel angles )

Ditto, running light

35 average
10

10-3
293

...

• connected, steel
wheels. j

45
12

13*3
340

) Drive, direct spur-
r connected, steel
I wheels,

Battery of 4 Radial Drills, broaching ) |

out f holes to}" f. '5

Ditto, running light 1 5

44* 2-^
1-48

/Drive, direct spur- '
1 geared to under-
4 ground shaft. :
Machines bevel j
( geared to shaft '

Stancheon Facing Lathe, facing \ '

stancheon one tool |" cut x i\," \ 10
feed ) j

Ditto, running light ' 7

2.93 ' -87
206

) Drive, direct spur-
- geared to hiad-
1 stock.

Horitontal Drilling Machine, drlUlng ;
i" hole. 160 revs., twist drlU ... i

Ditto, running light

10
5

293
1-48

368
148

. Belt drive.

Joist Milling Machine, milling 10" x »
5"R.s.l i

Ditto, running Ught

1 Drive, direct spur-
j geared to machine. 1

In the above list the amount of power consumed by the machine is shown,
also the actual power consumed in doing useful work.

Stewart

190^.] APPLICATIONS OF ELECTRICITY: DISCUSSION. 1006

crane-load is very considerable, in comparison with the machine Mr. Aitken.
and lighting loads, it is advisable to run the lights off a separate
generating set. Fig. A. shows a tracing from recording ammeter card
for 24 hours. The sudden fluctuations are caused by the stopping
and starting of the electric travelling cranes, which are of the three-
motor type and for six-ton loads.

With regard to polyphase working, the variations in speed and
torque in an engineering shop are so great that one is compelled to
decide in favour of the continuous current, in spite of the incon-
veniences of the commutators, until such time as the pol3rphase motors
can be made to do what continuous -current motors will do.

Mr. Andrew Stewart (communicated) : The comprehensive nature ^^^J^j!^'^^
of up-to-date electrical engineering makes it difficult to give the
specialist in one particular, branch of the industry a very frequent
innings ; considering the importance of electric motive power, the
papers which have just been read on the subject will put on record
much that is valuable. Mr. Chat wood's preference for direct currents
must, I fear, be due more to a lack of acquaintance with multiphase
currents, than to any disadvantages which are inherent in them ;• cer-
tainly the cases which he cites, are those in which constant not variable
speed is required. Under these circumstances, surely the author will
not argue that direct currents have any advantages over alternating ;
indeed the latter are just the proper thing in the cases under considera-
tion. That the author should condemn the adoption of four motors in
preference to one, because on paper a balance of 2J per cent, per
annum can be shown in favour of the latter is, one might think, a little
dogmatic. There might easily be collateral advantages which cannot
often be accurately expressed in £ s. d. that would overbalance the
small difference ; if part of the works made even a very small amount of
overtime, judicious grouping to several motors would easily turn the
balance in favour of more than one motor.

The gUmpses which we get of the efficiency of some modern direct-
current motors, is a striking commentary on the result of unlimited
competition ; the motors may be mechanically strong, but what
engineer who has been engaged in testing them can say that equal
progress has been made in efficiency ? Of course the idiosyncrasies of
the purchaser have had something to do with this ; people seem to want
a motor which is as invulnerable as a modern ironclad, and with as
little hum as an empty beehive, yet as cheap as possible ; something
must be sacrificed, and efficiency is frequently offered as a sacrifice
to the other and more desirable (?) features.

Mr. Williamson gives us a paper which from a practical point of
view could scarcely be beaten. To the man who installs large power
plants many of his deductions are not new, while others permit of
different views. Not every one has been so fortunate with chain-drives
as the author seems to be, but the performance of these are chiefly
governed by environment ; there are many cases where they may be
employed in place of worm or double-reduction spur-gearing, though
where the ratio of reduction and space permits, single-reduction spur-
gear would be hard to beat. There are, however, cases when it seems
Vol, 82, 67

1006 WILLIAMSON AND C HAT WOOD : [May Uth,

Mr. Andrew reducing gear is scarcely justified at all. Take cases where moderate
*^ ' speeds of 500 to 650 revolutions per minute are required, and horse-powers
of 5 to 10 or 15. In how many cases can one find high-speed motors with
spur-gear used, even where considerations of space are not paramount ?
Taking motors of the aforementioned horse-powers and comparing
slow-speed motors of 600 revs, against high-speed motors of about
1,300 revs, with spur-gear, the efficiency is in all cases about 6 per
cent, in favour, of the slow-speed motor, while the capital cost is only
10 per cent, in favour of the geared motor. Considering that a 15-H.P.
motor using energy at id. per unit can in a year take electrical
energy to the value of twice its capital cost, the small extra interest
charge involved in the slow-speed motor is saved from 8 to 10 times over
in . a single year ; yet how many examples of geared motors can be
found, with nothing except lower capital cost to justify their existence.

The variable-speed motors which the author mentions on page
937 are not by any means new, but the limit has hitherto been set at
much less than 100 per cent, increase, due chiefly to sparking diffi-
culties. Perhaps he can tell us if commutation takes place under a pole
horn maintained at constant strength by some means ; it does not
appear likely that satisfactory commutation can be obtained without
some special commutating device. The switch Mr. Williamson men-
tions does not seem to present any difficulty, and has been used for
this purpose before ; the patentable features should certainly prove
interesting to the men who have for years been engaged on problems
connected with speed regulation.

The crane speeds which the author gives are of more than academic
interest ; nothing is more conducive to economy in engineering and
shipbuilding yards than the rapid handling of heavy weights. Who in
charge of a shop has not seen expensive machines, almost equally
expensive skilled workmen, and a small army of labourers idle, while
a steam or rope-driven crane crawled down the shop with the work ?
Such a spectacle never fails to raise the back of an employer, and by
directing attention to this aspect of the question, one is more likely to
succeed in convincing works owners of the advantages of electricity
than by means of the mathematics which Mr. Chat wood has inserted
in the closing pages of his paper.

The question of a spare plant in a works generating station is raised
by Mr. Williamson, and it is remarkable how central-station practice
has stamped itself on many installations. It may be questioned
whether, in many works, the outlay of 20 per cent, of the capital on
spare plant can be justified. The works owner must first of all be
convinced that electricity is quite as rehable as his old plant, and if he
is told that a certain proportion of his generating plant has to be in
duplicate he will not feel reassured. He argues, not unreasonably,
that he docs not at preseiit duplicate his boilers and engines, and
cannot see, if electric power is quite as reliable, why he should put in
spare generating plant. Many works get along quite well on no spare
plant ; I have been connected with several works plants from 200 to
1,000 H.P. where no spare plant has been installed, and in two cases
six years' running has not yet shown that any risk was involved in

190».] APPLICATIONS OF ELECTRICITY: DISCUSSION. 1007

dispensing with the spare plant, even where in one case a night and Mr. Andrew
day shift is the rule : such repairs as have been necessary in the ^*®^*'^*
generating station have been executed during week ends and holidays,
just the ordinary factory routine.

The table of costs per unit emphasises what has been recognised by
engineers engaged in power work, viz., that no plant over 200 H.P. can
afford to buy its energy ; wholesale power generation is cheap, but it
costs too much to deliver it at the factory. Capital charges on mains
and sub-station plant unduly burden the large undertaking, while the
losses in transmission and transformation have also to be reckoned with.

A works of any size can purchase coal almost as cheap as the large
generating station ; it can put down its generating plant at almost the
same cost per kilowatt, and if it does not generate as cheaply, the
difFerence is only a very small fraction of a penny per unit.

Mr. H. O. Wraith {communicated) : Mr. Chatwood gives tables Mr.Wraiih.
stating the maximum brake-horsc-power required for certain tools, but
these figures do not really give any useful information, for so much
depends on the feed and speed, that is to say on the amount of metal
' removed in a given time. Only within the last week I was in commu-
nication with a firm (not electrical engineers) who had been inquiring
for large lathes, driven by separate motors, and the sizes of motors
quoted for by various toolmakers varied from 4 H.P. to 120 H.P., for
what was nominally the same lathe. The reason for the discrepancy
was that the firms quoting low-powered lathes were offering machines
which would only remove perhaps one-tenth of the metal in a given
time that the higher-powered lathes would. The firm offering 120 H.P.
made no mistake about being able to do the work required.

It would be interesting to hear if the author of the paper has taken
any tests on the basis of measuring the actual work done by the
machine-tool. I think the figures the author gives as to grindstones
used for dressing, etc., are, for this class of work, rather low, and I
should be sorry to put two great hulking seven-foot grindstones used
for these purposes on one poor little 15-H.P. motor in a shop where
any attention is paid to getting work out quickly, and therefore cheaply.
It is the usual thing for the grinder, when dealing with long bars,
to sit on the bars when grinding, so as to get more weight on, and I
have often seen a single grindstone take 13,200 watts, or roughly 15
H.P., when grinding bars, say, two and a half inches wide.

The method of starting grindstones and similar machinery with
heavy moving parts by means of a magnetic clutch is very ingenious,
but has Mr. Chatwood any experience as to the wearing qualities of such
a clutch ? for my experience of clutches is that the cost of renewals,
adjustment, and repairs more than overbalances their advantages. It
appears to me that a simpler and better method is to have a shunt
motor with a few series-turns on, a starter of some form that is not
likely to take any harm from being overloaded now and again, for
preference perhaps a liquid starter, and see that the man who starts the
motor knows what he is doing, and starts slowly. The arrangement the
author proposes is very susceptible to injur3Mn incompetent hands, more
so than the simpler arrangement above, where about the worst a man

1008

WILLIAMSON AND CHATWOOD ;

[May 14th,

Mr. Wraith.

Mr.

Cbatwood.

can do is to blow the fuse, and, unfortunately, in the majority of places
it is very difficult to keep electrical machinery out of incompetent hands.
Mr. Chatwood recommends the use of storage batteries in private
stations of considerable size. Has he any figures in support of this ?
The difference between the ordinary day-load and, say, overtime
load may be great, but in an installation of any size the percentage
of variation of load during ordinary working hours is very little, and if
the installation has been properly designed, the generating plants are
of such a size as to fit in with the different loads at different periods of
the twenty-four hours, so that whatever generating plant is running, is
running as near as possible to its maximum and therefore most efficient
load. The battery is only occasionally useful and economical, on small
overtime loads, and taking into account its heavy first cost, space it
occupies, and large depreciation, I think there is no doubt, in nearly
every case, it is not worth putting in, and that it is cheaper in the long
run to keep an engine running for overtime, except perhaps in the case
of offices, which hardly come under the head of machine shops, or
where there is a lot of Sunday repair work done, which would necessi-
tate, in the absence of a battery, firing up a boiler. Such places where
Sunday work is done are, however, few and far between, and in such
cases a better solution of the local problems would probably be found
in a gas-driven plant.

Mr. A. B. Chatwood {in reply): Before I reply to one or two points made
by speakers in the discussion, I should Hke to congratulate Mr. William-
son, first on having had the opportunity of dealing with works such as
those described in his paper, and secondly on having had the unselfish-
ness to give us experimental results such as he has done in his paper,
of which I do not think we can fully appreciate the value here and
now. It is in the months to come that we shall find out how valuable
they are, when we use them constantly for reference. On pages 934
to 936 of Mr. Williamson's paper he speaks of the driving cost
differences with various groupings of a certain number of lathes, and
he says the working conditions would be fairly represented by assuming
eight out of ten machines to be in use, the remaining two having tools
or work changed or set. Unfortunately my experience has not lain
in shops where that statement would be at all true. The probable
working conditions in these shops are that about two tools out of ten
would be working, and the advantage, therefore, in those cases of a
divided drive would be very mucli more pointed than is shown by
Mr. Williamson. Mr. Allen has explained to us a method of driving
which, personally, I had not come across to any extent, but I think
that in the bulk of small shops the 25 per cent, which he put down as
a saving would be a long way off the mark, because the abolition of
counter-shaft arrangements and belts off the line shaft would, I think,
cause a saving of very much more than that — at any rate, in shops such
as I have been speaking about. Mr. Scott called attention to a matter
that is mentioned I think, in both the papers that were read— that is,
to the use of a flywheel or a very large armature. I do not think that
its importance can be very much exaggerated in some cases with
reversing machines and with machines with intermittent load. He also

19(W.] APPLICATIONS OF ELECTRICITY: DISCUSSION. 1009

spoke at some length on three-phase plant, and Mr. Patchell made Mr.
some remarks about it. I have been for the last two or three months
carrying out experiments in a cotton mill in order to determine a good
many points that never have been determined as far as one can find
out, about driving cotton machinery electrically, and I think I may
say that in all probability the mill is going to be driven electrically.
It is a small Bolton mill of 125 H.P., and one of the great objects of
going in for the conversion to electric driving is the doing away with
all the bother of having driving plant of any sort to look after. The
Corporation of Bolton can supply either single-phase alternating
current or direct current. This mill, I need not say, will be driven
by direct current. At the same time, I have no doubt whatever that
if electric driving spreads into the cotton mills of Lancashire, three-phase
plant will be put down, and I think very likely some go-ahead towns —
such as, perhaps, Bolton — will go in for supplying three-phase current
specially for mills at a price considerably under a penny. But I do
not think that three-phase motors are universally applicable for driving
machine tools. One of the very great advantages of electric driving
is the question of delicate speed control, and of not being compelled
to jump from 200 to 400 revolutions, or from 400 to 800 revolutions,
or anything of that sort. Personally, my experience with polyphase
motors is that up to the present they are certainly deficient in speed
variation. Mr. Scott advocated the use of long cones and belts to get
over the difficulty of delicate speed control with the polyphase motor,
and he said that belts were good enough for our grandfathers and
they were good enough for our fathers, and I understood him to infer
that therefore they are good enough for us. I think the object of
having papers at this Institution is to advance a little on what our
grandfathers did. I do not want to say very much about our grand-
fathers and fathers ; they were very good people in their way — at least
mine were — but I have spent some eleven years in connection with
works where that principle was carried out, and I must say that, as far
as one's work was concerned, I never had such a miserable time.
Mr. Scott also spoke about armatures burning out. I have had
experience of a good many motors, and I have had, in machine-tool
driving, one case of an armature being burnt out. I was not very
much surprised about it, because it was a motor that I built myself
for experimental purposes about fourteen years ago.

Dr. Rhodes has somewhat mistaken the view I attempted to express
at the end of my paper on the question of generating current. I most
cordially agree with him in saying that where the demand is large it is
better to generate one's own current. The point 'which'I wanted to
enforce in my paper was simply, that if you can purchase current from
an outside source as cheaply or nearly so as you can produce it yourself,
then it is better to save the worry of having another department to look
after and devote the portion of your energies thus saved to increasing
your own particular business. I do not think that in any of the
particular cases given in my paper, especially as none of these shops
have any electrical people at present, Dr. Rhodes would advise genera-
tion on the premises.

1010 WILLIAMSON AND CHATWOOD : [May 14th,

Mr. I can quite believe Mr. Wraith's statement as to the various powers

^****^ quoted by tool makers for the same lathe, as I have experienced a case

in which the tool maker who built a machine stated that a 6 H.P.
motor was big enough for it ; a 40 H.P. was put upon it, and this has
been replaced by a 60 H.P. Quite apart from this ignorance of some
tool makers, the cutting power of what is nominally the same lathe by
different makers varies enormously.

Tests of the nature suggested by Mr. Wraith hardly come within
the scope and object of the paper, which was intended rather to point
out what is actually taking place in connection with electric driving
installations of small shops carried out by men absolutely ignorant of
the subject, and to point out some, at any rate, of the numerous factors
which should influence the arrangements of any particular case. I can,
however, give the figures obtained on a 6-inch lathe during the course
of some experiments which I carried out on various samples of steel :
but I should not like any one to expect a result an)rwhere near this
in ordinary practice, as the circumstances were here entirely special.

The steel cut was i in. diameter bright drawn bar, cutting speed 50
feet per minute, tool }ths round silver steel very carefully treated, held
in a Smith and Coventry holder, cutting angle 55** 15' ; front clearance
y** 55'. Rate of cutting, 22*84 lbs. per hour. Power absorbed at tool point,
0-314 H.P.— equivalent to 72*6 lbs. of steel removed per hour per H.P.

The grindstones referred to in the paper are not used with the
object of removing as much metal as possible, but. simply for removing
rust and scale and for dressing small rivet heads : the powers given in
the paper have been obtained from actual practice. Where, however,
stones such as these are used for heavy work, as is the case in the
manufacture of textile machinery, the power absorbed will sometimes
surpass the figures given by Mr. Wraith.

Mr. Wraith is, I think, under a misapprehension as to the magnetic
clutch. The arrangement described, somewhat imperfectly perhaps, is
not a mechanical clutch magnetically operated, but entirely magnetic,
the two parts of the clutch being separated by a fixed small air-gap, so
that there is in the clutch itself no wear.

I must flatly contradict Mr. Wraith's statement that I " recommend
the use of storage batteries in private stations of considerable size." In
small shops such as those described in the paper the fluctuations of load
are considerable — from 2*5 to 9*3 H.P. in one case, from 4*6 to 23*6 H.P.
in another. The statement in the paper is, I think, rather a reminder
that it is desirable in each particular case to consider whether or not
batteries would be advantageous. So many local circumstances enter
into the matter, that it would be impossible to form any general opinion.

Mr. Andrew Stewart seems to have read the paper somewhat care-
lessly, as in the three cases cited specificially, pages 979 and 980, as
well as in the summary of the possible advantages of the installation of
electric driving, page 971, the advantage of variable speed is sufficiently
insisted on. I expressly stated, however, that in my opinion there was
no general question of alternating and continuous current, but that
every case must be decided on its merits.

I should like to point out that I did not condemn four motors instead

1903.] APPLICATIONS OF ELECTRICITY: DISCUSSION. 1011

Mr.
WUUamson.

■of one in Case 2 because of the slightly increased cost, but because Mr. ^^
** almost the whole of the shafting is to be driven and no one of the
advantages of electric driving is to be secured," and at the same time
pointed out that the cost would be slightly higher.

May I refer to the diagram given in the paper with regard to two
planing machines, as I think an analysis of them will give a clear idea
of what goes on in shops such as those discussed in my paper. The
power absorbed by the smaller machine when not actually cutting is
considerably greater than that absorbed by the larger, although the
speeds are slower, showing that the condition of the smaller machine
is such as to require examination. It is hard for men trained in
up-to-date shops to realise the conditions which prevail in shops which
were all right thirty years ago, but which have not advanced in any way
since.

I should like to feel that we, both as individuals and as an institution,
are doing all we can to influence manufacturers and their managers
to consider carefully every case of electric driving, and not to follow
the policy which has been followed in the shops noticed in my paper, a
policy which can only be described as " the shove-a-motor-down policy."

Mr. A. D. Williamson {in reply) : I thank you very much indeed
for the very kind remarks that have been made about my paper ; I think
almost too much has been said in that direction. If the paper is of
value, it is simply due to the fact that I have been in the position to
accumulate useful information. Now with regard to the discussion,
the first point raised was the question of breakdowns. I have thought
about it, but I cannot remember any serious breakdowns whatever.
We have had to stop occasionally — possibly for a hot rod, or something
of that sort — but dividing the plant in the way I have mentioned in the
paper, we have always had some spare plant to carry on, and it has
caused no stoppage of the works. If we had any trouble at all, it has
been not with the electrical plant, but with the steam plant — with the
boilers. I do not think the comparison between the large marine
engines and electric generating plant is quite fair, because a steamer
has to have one large engine— there is no help for it. If that breaks
down, the ship is stopped. That large engine is always working at
maximum load, and therefore at maximum efficiency. But if we put
one large engine into a works, that engine would have to work some-
times at only one-tenth of the full load, and therefore at very poor
efficiency. So the two cases can hardly be compared.

I do not quite follow Mr. Mavor's statement that the real argument
for adopting electric driving is " the possibility of introducing econo-
mical plant into the generating stations.*' I think rather that the
centralisation of the plant is the main argument. Whether the plant
be old or new, economical or wasteful, within reasonable limits the
cost of labour will not be altered. Coal and water are reduced by
economical engines, but these two items only represent about half the
cost per unit at the switchboard.

The economy of electric driving must be considered in terms of
useful work at the machines and tools. Replacing an old and inefficient
engine which drives direct to line shafting, by a new engine of high

1012 WILLIAMSON AND CHATWOOD : [May 14th,

Mr. efficiency and a dynamo and motors, will not reduce costs so long as «

the load remains high. It may, however, have a very marked economical
result if the load is a varying one and full advantage is taken of the
opportunity to cut out shaft and belt losses at times of light load.

There can be no general argument for or against electric driving ;
each case has its pros and cons,

I do not mean to suggest that economical engines should be passed
over, but I attach more importance to careful attention to the arrange-
ment of machine driving together with absolute reliability in the
generating station.

I quite agree with Mr. Selby Bigge. He says that the power-house
should be designed in proportion to the whole area of the works — that
is, to leave room, as I understood him, for all the generating plant that
is likely to be required at any time. That is what we tried to do. We
have not only extended the shops, but we have also bought more land —
when the first power-houses were planned, nobody could foresee that
The method of allotting space for power-house in recent cases was to
take the total acreage of the land, and from the figures which are
published in the paper to estimate what is the maximum amount of
power required to drive all the machines which we could put into the
buildings covering the whole of that ground. Those figures in the
paper will be found fairly accurate for works of a similar nature. It is
not always possible to get as much space as one would like in a central
position to put down the plant. That is why we had to divide it and to
have two or three separated stations. Then about the insulation on the
overhead wires. We provide a light insulation, as I say, chiefly for
the protection of the telephone wires, which have an unfortunate habit
of falling, and when they come across the power wires there is trouble
and the telephone service is interrupted. After six years we find that
none of the light insulation has come ofiF the wires, and it is apparently
in a perfectly good state of preservation. The recent machines which
we have put down, within, say, the last year or two, are nearly all
designed for variable speed. It is becoming much more common now
than it was to have variable speed. I think that is chiefly due to our
having found out the extreme convenience of it. I have spent a good
deal of time looking about for alternating-current motors which possess
the quality we have been hearing about of a large range of speed
variation, but I have really never come across a practical solution of
that difficulty yet. I have been in most of the Continental electrical
works and manufactories, but I have never come across a case which
was seriously described as a practical solution of the difficulty. I am
very pleased to find that every speaker has agreed on the question of
circuit-breakers. They were a constant source of worry to me at the
works, fuses with a liberal margin are very much better. As regards
saving in the works, Mr. Selby Bigge put it down roughly at 35 per
cent. Curiously enough, I have worked out a number of cases where I
could get fairly reliable data, and I came to exactly the same conclusion
that it was between 30 and 40 per cent. You may take it as 35 per
cent, on the average when you are dealing with works of this nature.
When we started to put down this plant, we had to choose between

1903.] APPLICATIONS OF ELECTRICITY: DISCUSSION. 1013

alternating and continuous current. Of course, at that time there was Mr.
very little comparison between the two.

There is no doubt that improvement has been made in alternating
motors, but I do not think that they compare for our class of work — for
solid engineering work, where you want a very heavy starting torque in
the case of cranes and shop machines with flywheels, which take a great
deal of starting, and also with machines requiring speed variation. I
think those two points are most important, and I fail to see where the
advantage of 3-phase work comes in when you are deaUng with short
distances, and where, if you use 3-phase plant, you would not exceed the
pressure which you use for continuous. I think it is a positive dis-
advantage, because, if I had 3-phase machinery in the works, I should
feel tempted to put transformers in, in order to get two or three different
pressures, and by doing so, of course, would throw away a certain
amount of energy. I agree with Mr. Allen entirely on the question of
clutches. We have used clutches in a number of cases and found them
exceedingly good, but six or seven years ago we had a difficulty in
getting them. Mr. Fairfax spoke of the speeds we have chosen. We
had to choose those speeds, averaging about 600, as a compromise
between the excessive cost of low-speed motors and the difficulty of
reducing high-speed motors down to the point where you would wish
to use the power. This is a very interesting gearing indeed which he
has brought forward to-night, but I am afraid that to get only a differ-
ence of speed of from 800 to 650 on four pulleys side by side would not
meet our requirements in all cases. This model seems to run very
nicely, but for most tool operations we require a much wider range of
speed. Mr. Russell, speaking of the Silvertown Company, says there are
a number of cases where it would not do to put in motor driving and
displace engines which are there at present. I quite agree with that in
general. In many cases there are operations which are much more
economically done by steam-engines, taking into account the
capital outlay involved in electrical driving arrangements. In our
own works we started with that idea and modified it a great deal,
because we found that by putting on every machine at all suitable for
electric driving, we increased the load on the generating plant and
secured a steady demand for the current, thus reducing the cost per unit
very considerably all round. When a fresh operation was put on to the
power plant, although it might not be done any cheaper than it was
originally, yet by increasing the load at the generating station, and
dividing the standing charges between many more units per annum,
we found it cheapened the cost of production on all the other operations
about the works. In considering the cases of applying motors to a works
like the Silvertown or any other works, it is very important to take into
account whether labour can be saved or not. It is a question of
reducing the staff of engine-drivers and firemen to a great extent.
It is not so much a question of an isolated engine as of an isolated
boiler— that is the trouble that has to be got rid of. With regard to the
worm-gearing which is used in the Silvertown works, I have had
experience of. fairly heavy power worm-gearing under exactly similar
circumstances — that is, in indiarubber works. I had tests made there

lOU WILLIAMSON AND CHATWOOD : [May 14th,

Mr. of it, and the efficiency came out between 85 and 90 per cent. Ball

anuon. ^jjj.yg^g were used, and of course it was fairly modern gear, very well
made and running in oil, and it had a long life. There was absolutely
no fault to find with it for that special work. It is too expensive for
ordinary work, I think, and not quite as efficient as spur-gearing. I
quite agree, also, that chain-gearing costs at least 50 per cent, more than
spur-gearing, but it has so many advantages that I think it is worth
paying for it in many cases, in order to get a compact drive.

I did not mean to speak disparagingly of smooth-core armatures,
because we have five or six smooth-core machines now of about 250
horse-power, and though they have been running for six years they have
not cost anything at all for repairs. But as we can buy slotted arma-
tures for much less money than we gave for these old smooth-core
machines, I much prefer to have slotted ones, because they are
undoubtedly stronger. In the early days I had a number of cases of
the armature conductors being swept round the face of the core, in
smooth-core motors, subjected to heavy variations of load. We have
had no troubles of that sort with any generators, though in the six years
we have had them they must have had a good many short-circuits.
Coming to Mr. Scott's remarks, my experience is practically confined
to continuous currents, and I have done very little with alternating
currents ; but as far as my continuous-current experience goes, it is
totally different to Mr. Scott's. We do not have to continually renew
carbon brushes, and we are practically unaware that there is a com-
mutator on the machine — it gives no trouble. There is one point that
Mr. Scott raises, and that is the comparative space occupied by the
continuous- and alternating-current motors. Mr. Scott says you
can put an alternating-current motor in a space into which you
could not get a continuous-current motor. Does that include the
speed cone that Mr. Scott recommends for varying the speed ? I
should think probably not. The question of gas-engine plant was
mentioned. It is only recently that we have been able to get a big
gas-engine. We are adding some gas-engines now, and if we had
work to do again of a similar nature we should put in gas-engines
without a doubt. We are at present building some very large
generators for a works in Glasgow, which are to be driven by gas-
engines at slow speed. When the plant is big it pays to put down
Mond gas plant, but if you have got a small plant it does not pay. To
reap the full benefit of all the bye-products in connection with the
Mond gas plant you must have a fairly big plant to deal with. Mr.
Hammond mentions the high consumption of coal. That has troubled
me a great deal, but I cannot help it. Those are the figures. I think it
is partly due to having small sets, and then in the case of the North
Power-house we are non-condensing. Another way I account for
the high cost is that we have steam-driven auxiliaries — the feed-
pumps and the condensers being driven by steam. There is no doubt
that these small auxiliaries when they are steam-driven eat up a great
deal of steam, and steps are being taken at the present time to replace
this steam auxiliary plant by electrically-driven plant, and when that is
done I am pretty sure that we shall get this objection removed.

1908.] APPLICATIONS OF ELECTRICITY : DISCUSSION. 1016

I do not think that the load-factor plays such a very important part Mr.
in fuel-cost. Consider the two cases of a perfect load-factor and
that at the Sheffield Works. The first would be represented by
a continuous electro-chemical process when the steam consump-
tion would be steadily at its minimum, say 15 lbs. per B.H.P. hour
for condensing engines of 500 B.H.P. The load-factor at Sheffield
is of such a nature that we can only run generators up to, say, an
average of 75 per cent, of full load, allowing a margin for fluctuations
in demand. Our steam consumption would not be more than 16
lbs. for the same size of unit This difference is only about 6 or 7
per cent., and would only raise the coal per unit from o*3d. to o'32d.
To go further, lighting stations have a far worse load-factor, but
their sets do not usually run at a lower mean load than 75 per cent., so
that during the time they are on they work as efficiently as the sets in
the steel works. No doubt some additional loss is made in lighting
stations, by having to light boiler fires and keep them banked waiting for
load, but my point is that load-factor affects coal consumption very
little, while it affects wages and standing charges largely.

The calorific value of the coal used at Sheffield is 12,720 British
Thermal Units, this being a mean of five kinds of coal.

Replying to Mr. Stewart's question as to the means adopted to secure
sparkless commutation with weak field, I may state that no special form
of pole-tip or commutating device is used ; the main principle of design
is to make commutation as natural and easy as possible. There is no
question that perfect icommutation is secured over the ranges of speed
mentioned, and that with very little addition to the weight compared
with a constant-speed machine whose speed is, say, midway between the
maximum and minimum of that of the variable-speed motor.

Mr. Stewart is right in saying that variable-speed motors are not new.
I have used them ifor six or seven years, although it is only within the
last four years that I have made full use of the convenience of variations
of 200 or 300 per cent, in speed.

Mr. Chatwood says he thinks that two machines working out of ten
would represent working conditions more fairly than eight out of ten.
If we found that to be the case in our works, we should look out for some
new foremen.

The President : We have certainly had very interesting papers The
from both these gentlemen ; they are papers which I think do an ^«*^**«"*-
Institution like ours a great deal of good, because they teach the
outside world what they ought to know — viz., that electrical current
can be used to great advantage in many cases where the public may think
its adoption of doubtful utility. It is quite needless, aiter the full and
interesting discussion that has taken place, for me to say anything,
because I can see by the way that you have listened to the remarks of
Mr. Williamson and Mr. Chatwood, and also to the gentlemen who
have discussed the papers, that we are very much indebted to them
for what they have done for us. Without further words I ask you to
show your appreciation in the usual manner.

The vote was carried by acclamation.

1016 ELECTIONS. [May 14th.

THE RICHMOND-CAREY LIFT.

The President : Before you go, gentlemen, I have to say that
Mr. Carey has been kind enough to bring here a model of the Rich-
mond-Carey electric lift. The time at our disposal is now very short,
and there is no paper to be read on the subject. Mr. Carey, in making
his demonstration of the working of the lift, will give us a short
explanation which will only occupy five minutes.

Mr. R. F. Carey : The lift of which the model is before the meeting
is a new electric lift which I have got out in conjunction with Mr.
Richmond. The idea of it is to do two things — first, to get a lift
which will work automatically, and, secondly, to get one which, as far
as wc can see, is absolutely safe. I do not know whether any one can
point out how it is possible to have an accident with-it. I have tried
to find out, but cannot do so. There are no attendants required. No
one can open the outside doors and fall down the well-hole, because
the doors can only be opened when the lift has come to a standstill on
the particular floor. That avoids the most frequent cause of accidents.
By pressing a button the lift comes automatically to the required floor,
stops, the door is freed, the passenger steps in, and, by pressing one of
a series of buttons inside the car, directs the car up or down to the
floor to which he desires to go. There the same process is followed ;
the car stops automatically, the door is unlocked, and the passenger
steps out. It is worked in the ordinary way by an ordinary motor and
gearing.

Mr. Carey then showed the model in operation and explained a
diagram which he exhibited.

The President : I awi sure, gentlemen, that you wish that I should
thank Mr. Carey in your name for bringing this lift before us.

The President announced that the scrutineers reported the
following candidates to have been duly elected : —

Associate Members.

William Alfred Barnes.
Joseph Wm. Aberdeen Binner.
William Dolton.
Henry Francis Francis.

Herbert Vickers.

Associates.

Joseph Menmuir.
Albert Edwin Moore.
Geo. Richardson.
Arthur Robert Shapley.

Cecil Edward B. Christie. Samuel Scargill.

Chas. E. F. Evans. ' James Stephen Souter.

Wm. Hellier Evans. Percy Alfred Spalding.

Robert Pries. Herbert James Stracey.

Students.

Richard Chas. Hope Dawes. | Henry Arnold Greaves.

Wm. James Lindsay.

1903.] MOUNTAIN : ELECTRICITY SUPPLY. 1017

LEEDS LOCAL SECTION.

ELECTRICITY SUPPLY FOR SMALL TOWNS
AND VILLAGES.

By A. B. Mountain, Member.

(Paper read at Meeting of Section^ March i% 1903.)

The success which has attended the introduction of electricity to all
large towns is indisputable, and that it is being adopted for lighting and
motive power at an ever increasing rate is also undeniable, but when
we consider the small towns and villages we find very little progress
has been made, and when we think of the immense number of such
places, many without even a gas supply, we must realise that there is
still a great field open to the electrical industry, but the fact that so
little has been done shows that difficulties and misconceptions exist
which are tending to impede the introduction of electricity, and it may
be well to consider these, first, from the point of view of influential
gentlemen residing in such small towns, whose support is necessary
for the introduction of any new undertaking, and, secondly, from the
engineers' point of view.

The first difficulty is the want of enterprise or energy which is
noticeable in all small places, not necessarily due to want of knowledge,
but rather to a desire to leave things as they are. This feeling of apathy
is greatly encouraged by the local gas companies, who are, perhaps
naturally, in opposition to the rival undertaking, and do not yet realise
that the introduction of electricity nearly always leads to an increased
consumption of gas.

The second difficulty is the supposed large initial outlay of capital
necessary to construct works, the very general idea that such small
works must charge a high price per unit, and so cannot compete
successfully with gas or oil, and will therefore not be carried on
profitably, and will consequently, if owned by a company, pay no
dividend, or, if owned by the local authority, become a burden to the
ratepayers.

It is perfectly true to say that several small places in which works
have been constructed have not been financially successful, and that
care must be exercised in the designing of the works and mains to
ensure success. The causes of failure would appear to be due to the
small towns constructing works upon the same lines as neighbouring
large towns, or, in other words, such failures have been due to want of
knowledge, but with care in the selection of a system and in designing
the works and distributing mains financial success can be assured even
on the smallest scale, and the initial capital outlay upon works in a
small place should be proportionately less than in a large town where
one is compelled to construct works and lay mains of sufficient size to
meet the demand which is certain to arise in future years, and which

1018 MOUNTAIN : ELECTRICITY SUPPLY FOR [Leeds,

necessitates a large proportion of the initial capital being unproductive
for some years. Then, again, it is wrong to assume that small works
cannot sell electricity profitably at a reasonable price per unit. In
many small places, both under the control of companies and local
authorities, the charge is at the rate of from 4d. to 6d. per unit, and,
in some small villages where the supply is derived from local works
such as collieries, mills, local electrical engineers, etc., the supply is
being given at prices varying from 3d. per unit upwards, and in many
cases, where the supply is being taken from the gas or oil plant installed
for a private residence, a charge of 4d. per unit would be profitable.

There is also the further fact that the charge for gas in small towns
is usually much higher than in large ones, so that the electricity supply
would have this great advantage in small places. It is usually found
that electricity at 4Jd. per unit will l>e adopted in preference to gas at
2s. 6d. per 1,000 cubic feet

The third point against local enterprise is the idea that the power
companies will eventually supply all such small towns and villages, and
will consequently ruin any local undertaking. Undoubtedly, during the
last three or four years, a great deal of discussion has taken place, and
the idea has been very generally spread that the power companies
contemplate supplying over the whole of the areas for which they have
ParUamentary powers, but this does not seem probable or possible,
commercially, if one considers their past achievements, and the fact
that the small villages and towns are so far apart that in most cases the
mains required to connect two places will exceed the cost of construct-
ing and working a generating plant. In fact, it is difficult to see what
advantage can be gained by taking energy in bulk from a power corn-
company. In any case consumers will require meters and services,
mains will require laying from some central point to such consumers,
a building must be provided into which the mains would be carried,
and in which the alternating motors and continuous-current dynamos
will be fixed. This practically covers all that will be required for a
local central station, with the exception that steam, gas, or oil engines
would be substituted in place of the alternating motor ; in both cases
practically the same supervision and labour would be necessary. The
difference in cost would be that energy from the power company would
probably, in accordance with the latest published information, cost a^d.
per unit, whereas it could be generated by steam or oil engines at from
id. to id. per unit.

The fourth and perhaps most usual difficulty is the cost of obtaining
the necessary Parliamentary powers to establish local companies or
municipal undertakings, and a further dislike to the stringent regulations
of the Board of Trade and the Local Government Board. These difl&-
culties appear to affect municipalities more seriously than companies,
but in any case are not such as to cause any trouble when the works
are once started. The fact that the Local Government Board will not
allow the cost of obtaining a provisional order to be placed to capital
account necessitates a charge upon the rates, and the additional fact
that the repayment of all money borrowed must commence at once is a
very serious point, and greatly retards new works, because it is practi-

1903.] SMALL TOWNS AND VILLAGES. 1019

cally impossible to get sufficient consumers connected during the first
year to bring sufficient revenue to provide the amount required to repay
the first annual instalment of capital ; consequently this amount, if not
provided by revenue, must be provided by rates.

That some concessions on this point might be made by the Local
Government Board is generally agreed, and when it is considered that
in the case of tramways one or two years are allowed for construction,
and that the full revenue from a tramway system commences at once,
whereas the revenue from an electric supply undertaking can only grow
gradually, it will be agreed that local enterprise is not encouraged.

Engineering Difficulties.

In considering the supply of small towns and villages from the
engineers' point of view, it is necessary to try and gather what small
amount of data exists, and consider the problems as quite distinct from
the supply of large towns.

The expression "small town" should include any place having a
population of from 5,000 to 15,000, and "villages" any place having a
population of from 500 to 5,000.

There are in Great Britain and Ireland about 500 such small towns,
and between 2,000 and 3,000 villages, and very few of these have any
electricity supply undertakings, so that there are plenty of opportunities
for activity in developing local enterprise.

The chief points which we, as engineers, should determine to enable
us to design a small scheme upon sound ^ancial lines are : —

1. The probable number of consumers and consuming devices which
will be connected within two or three years, and the ultimate maximum
development.

2. The maximum demand which the generating plant will be required
to supply.

3. A suitable position for the generating station, the form of motive
power and system of generation.

4. The best method of distributing the supply, and the connection
of consumers.

The first point is by far the most difficult, and nothing but experience
will enable one to estimate at all correctly, but it is most important,
because the works should be constructed so that extensions do not
mean scrapping plant in future years, and on the other hand the works
must not be unnecessarily large, or the financial results will be unsatis-
factory during the first few years.

It is also quite impossible to form any correct idea of the consumers
who will be connected without first settling the price to be charged ;
obviously, the lower the price, that is to say, the better the price
compares with gas, the quicker will consumers become connected,
but this course will also probably result in a loss for the first year or
two. There is little doubt that it is advisable to fix the price as low as
possible at the start and encourage all classes of consumers.

One method of ascertaining the number of consumers likely to be
connected is to graduate the number of premises by their rent or

1020 MOUNTAIN: ELECTRICITY SUPPLY FOR [Leeds,

rateable value, and it will usually be found that the majority of
premises rated above a certain amount may, with a few exceptions,
be relied upon ; the amount selected will vary in proportion to the size
of the town. If, however, the electricity supply is in the hands of a
company which would adopt some system of fixing prepayment meters
and a few lights free of cost, it might be possible to connect a very
large number of small consumers. Unfortunately a local authority has
no powers under the Electric Lighting Act to charge to capital the cost
of fixing wiring upon consumers' premises ; some of the larger towns
have obtained powers by applying to Parliament, but this course would
be altogether too costly to be undertaken by a small place.

The second point is more easily determined. In small places shops
do not indulge in a large amount of show, and fewer lights are fixed
generally. The maximum demand upon the works would not appear
likely to exceed, during the first two or three years, half the lamps
connected, and this would gradually be i;^duced to about one- third
of the total lamps connected ; this is assuming that electricity is
used for street lighting — if not, the maximum demand would be re-
duced.

The third point, the selection of the form of motive power, has in
many cases given the author considerable trouble.

The selection of a site for the generating works is not difficult, if
one first decides upon the kind of motive power to be adopted. If
steam is to be used, it is necessary to bear in mind facilities for getting
in coal, and water should be as near as possible for condensing pur-
poses. If gas is to be qsed and the supply taken from an existing
company, the position of the site must be such that the supply of gas
may be easily and cheaply obtained. If, however, it is thought advisable
to make your own gas or adopt oil engines, then the site may be
selected in the very best and most central position.

In most small towns the disposal of refuse is becoming a more or
less serious question, and should have consideration in conjunction
with the supply of electricity ; this may influence very largely the
selection of the form of motive power to be employed, because if
Refuse Destructors are to be adopted the heat may be used for
generating steam, and the cost of destroying the refuse reduced by the
amount which will be paid for the steam used for producing
electricity. The steam thus economically produced is of great
advantage to the electricity department, as it enables a low charge
to be made for energy for motive power purposes.

The form of motive power to be adopted must therefore depend
upon local conditions to some extent The chief point to determine,
however, is with which form of motive power the most economical
generation of electricity may be obtained, and it may be interesting to
give some examples of the different kind of plants which may be
adopted for a small town with a population of about 7,000.

The estimated lamps connected during the first two years are
3,000 of 8 c.p., and the estimated connections at the end of about
the loth year 14,000 of 8 c.p. The first instalment of plant would
therefore require to be equal to about 60 kilowatts, and might be

1903.]

SMALL TOWNS AND VILLAGES.

1021

divided into one 20 kilowatt and one 40 kilowatt plant ; the latter sized
unit of plant being continued as the station developed.

Confining now our attention to the generation only, the works
would cost the following amounts, depending upon which form of
motive power was selected : —

Oil.

Buildings and foundations

Two engines, dynamos and switchboard
4 H.P. plant instead of accumulators ...

Town Gas.

Buildings and foundations

Two engines, dynamos and switchboard
4 H.P. plant instead of accumulators ...

Producer Gas.

Buildings and foundations ,

Two engines, dynamos, switchboard, and producer..
Accumulators

Steam.

Buildings and foundations

Two engines, dynamos, switchboard, and boilers
Accumulators

250

125
£hS5o

250

1,050

100

£iAoo

500.
i»375

;£2,o5o

750

I;475

175

;£2,400

For the purpose of ascertaining the average cost of generation
it may be safely assumed that in the second year 30,000 units of
electricity will be sold. The costs will therefore be, approximately, as
follows for each form of motive power : —

Oil.

Oil, used as fuel

Oil, waste and stores

Labour in the station

Repairs

Management, rents and rates ...
Depreciation, at 4 per cent.

Interest, at 4 per cent

Total cost of generation per unit sold, 2*59d,
Vol. 82. 68

•5 pence per

unit

•12

»>

•40

•20

•37

•5

>»

•5

1022 MOUNTAIN: ELECTRICITY SUPPLY FOR [I^eeds,

Town Gas.

At 2S. per i,ooo cubic feet, allowing 25 cubic feet per unit.

Gas *6 pence per unit

Oil, waste and stores *i2

Labour in the station '40

Repairs '20

Management, rents and rates ... '37

Depreciation, at 4 per cent. ... '45

Interest, at 4 per cent '45

Total cost of generation per unit sold, 2'59d.

Producer Gas.

3 lbs. of coke per unit, at i6s. per ton.

Coke '25 pence per unit

Oil, water and stores *20 „

Labour in station *6o „

Repairs -24 „

Management, rents and rates ... '37 „

Depreciation, at 4 per cent. ... -65 „

Interest, at 4 per cent '65 „

Total cost of generation per unit sold, 2*96d.

Steam.

10 lbs. of slack per unit, at 8s. per ton.

Slack

Oil, waste and stores

Labour in station

Repairs ,

Management, rents and rates ...
Depreciation, at 4 per cent.

Interest, at 4 per cent

Total cost of generation per unit sold, 3*37d.

From the above figures will be seen the enormous importance
of keeping down at the lowest possible point the capital expended. It
may be urged that it is unnecessary to allow 4 per cent, for deprecia-
tion, and the same amount for interest, as a local authority can usually
obtain twenty-five years for the repayment of its electric lighting loan,
and the annual amoimt to be set aside each year for the repayment of
the loan, allowing 3 per cent, for accumulating interest, would only
equal 2| per cent., and money can be borrowed by a local authority at
3 to 3 J per cent ; but it is much better to keep figures perfectly safe,
and the larger the amount provided for depreciation the sounder the
undertaking will be. It is also doubtful if a company could borrow
under 4 per cent.

•42 pence per

•20

•60

'24

•37

•77

1903.] SMALL TOWNS AND VILLAGES. 1023

It will be noticed thJit in the Oil and Town Gas stations small
plants are suggested for running the load from midnight until the
following evening. These plants are so perfectly made that they may
be safely left to run without any attention, and will be found to be
much more economical and reliable than accumulators.

In most small places where gas companies are in existence, it will
probably be possible to obtain gas at a lower jwice than 2s. per i,ooo
cubic feet, and then, when the works had been running for a few
years, it might be found more economical to use producer gas.

If steam is adopted, the locomotive form of boiler will save a large
amount of capital by dispensing with brick chimneys and flues, and it
will be advisable to run non-condensing during the first few years.
The figures given show the results in what may be called a middle-
sized small place ; in larger towns producer gas or steam would
compare more favourably, while in small villages town gas or oil
would have still further advantages.

It is not necessary to discuss at length the system of supply to
be adopted. In most small places a two-wire 200 or 220 volt con-
tinuous-current system would be most suitable; but in some cases
where long distances had to be covered, alternating currents at 200
volts, with step-up and step-down transformers, would be very
convenient and simple.

The main thing in designing a generating station for small places is
to try and simplify the working arrangements as much as possible, as
it will be impossible to employ highly-paid engineers to take charge of
the undertaking.

The next point which the engineer must consider very carefully is
the method of distribution. Most small places are scattered over a
considerable area, and the length of mains per consumer will be much
more than in large towns. Consequently a great effort must be made
to reduce the cost. This can readily be done if overhead wiring is
adopted, and in a small town of a rural character no argument of any
importance can be advanced in opposition, while the arguments for
overhead wiring are very strong.

1. It is much more economical.

2. More easy to keep in order.

3. Easy to substitute larger wiring when small wires are over-
loaded.

4. No disturbance of the pavement is necessary to connect con-
sumers or find a fault.

5. The cost of connecting consumer is very materially reduced.

To show the difference in cost between underground and overhead
construction let us proceed with the example already considered, and
assume there are 120 consumers connected and three miles of mains,
the sectional area being 'i of a square inch. With overhead wiring it
would not be advisable to fix such heavy cables in many streets at first,
as it could so easily i>e replaced by heavier cables later on if it became
overloaded.

1024 MOUNTAIN: ELECTRICITY SUPPLY FOR [Leeds,

Distributing System with Uxdergrouxd Cables.

3 miles of 'i single cables, laid in wooden troughing ... 1,290

20 cable connecting boxes 80

120 service boxes 240

120 services, including meters, fuses, and fixing ... 540

;£2,i5o
Distributing System with Overhead Cables.

3 miles of 'i conductors, fixed upon wooden poles... 770
120 services, including meters, fuses, and fixing... 480

;£i.25o

If we now consider the annual cost of distribution we see clearly
the immense advantage of overhead wiring from the financial point of
view.

With underground cables the cost per unit will be as follows : —

Labour '12

Repairs '16

Management, rents and rates '16

Depreciation, at 4 per cent '69

Interest, at 4 per cent '69

r82d.

With overhead cables the cost per unit will be : —

Labour "12

Repairs '16

Management, rents and rates '16

Depreciation, at 4 per cent '40

Interest, at 4 per cent '40

r24d.

If we add the cost of generation — 2*59d., the total cost of production
with the overhead cables becomes 3*83d. This is for the second year's
working. As the demand increased the cost of production would
decrease, so that we may reasonably expect to see small undertakings
working profitably and charging from 4d. to 4J<i. per unit.

It will be noticed that the cost of services, meters, etc., is included
in the above figures. It is usual to charge a sufficient amount for
meter rent to cover the interest and depreciation upon the capital
so expended, so that this item might be neglected, which would still
further reduce the costs of production, but on the other side of the
accounts will usually be found an allowance or discount if the accounts

1903.] SMALL TOWNS AND VILLAGES: DISCUSSION. 1025

are promptly paid, and this amount has been considered to balance
meter rents.

The staff required to work the gas-driven plant would be : —

One Engineer in charge at ;£i3o

One Assistant „ £68

One Junior „ ^£52

These would during the day fix meters and services and carry
out any extensions of the overhead wiring, and the time expended
upon such work would be charged to capital.

It is impossible to conclude a paper upon this subject without
pointing to the senseless opposition of many local authorities, who
obtain a provisional order for the supply of electricity and then spend
years debating the expediency of starting the undertaking, or who do
nothing until some effort is made to start a company, and then object
to the order being granted. It would appear that some effort must be
made to make the local authorities realise that they are responsible for
the backward condition of electricity supply in small places, and that
in the general interests of the country they must either take up the
business themselves or allow the supply to be undertaken by local
companies.

Mr. W. Emmott said that he was quite at one with Mr. Mountain in Mr.
his views generally, regarding the supply of electricity to small towns, Emmott.
and as to the causes of such backwardness. At the same time it was a
pleasure to be able to state from his own experience that matters were
improving in this respect, and he was glad to say that there was a
more healthy feeling springing up. The smaller Urban Districts and
towns were beginning to realise the fact that they had a valuable
property in their provisional orders and also that they could not go on
playing the " dog in the manger " for ever. Ratepayers were awakening
and the Board of Trade was beginning to let the small Councils know
that they would have to move or let some one else move.

He quite concurred in Mr. Mountain's remarks as to the assistance
we ought to obtain from the Local Government Board and the Board
of Trade. He had tried in three instances in 1900 and 1901 in which
they had provisional orders to get, to induce the Board of Trade to let
them insert a clause empowering the local authority to lease or sell
motors, and to do other things which came within the province of
electric supply, but unfortunately they could get no alteration or
assistance from the Board. This was so much a provincial matter
that the Leeds section of the Institution of Electrical Engineers ought
to do something in forming a Committee to take the matter up in
order to bring pressure to bear through the local Parliamentary repre-
sentatives with a view of getting the Board of Trade to give a little
more latitude in this direction, and he intended laying a scheme
before the Chairman with this end in view.

In the case of a large town like Leeds the expenditure of ;£2,ooo or
;g3,ooo in order to get a special Act of Parliament was as nothing, but
for a small place it was such a serious matter that they could not do it.

1036 MOUNTAIN: ELECTRICITY SUPPLY FOR [Leeds,

Mr. and these small places could not fight against what may be called the

anti-municipal tradmg section of the community, which, he thought,
carried things somewhat too far.

Regarding the large power schemes, he did not see what good they
would be to small places of say 10,000 inhabitants for lighting purposes,
unless it happened to be an exceptional place in regard to a day-load.
This opinion was confirmed by the report of Mr. Parshall just issued
with the Yorkshire Power Compan3r's prospectus, in which he noticed
that a plant capacity of 10,000 k.w. worked out at £S2 per k.w. for
capital expenditure, while the receipts for current sold came out at
£y los. per annum. Taking the average price to be obtained for
current at 2d., this equalised 900 units per annum per k.w. of plant
installed. He had made a theoretical load curve on this basis, and it
required no great mental effort to see that the small towns and villages
were not likely to be of use in making even the modest dividend of
5*83 per cent.

As to destructors his experience told him that where five tons of
refuse can be obtained per day it would pay to put down a destructor,
and part of the whole cost of this should certainly be borne by the
sanitary department, or this department would have to sink capital in
ground for a tip, and often pay more in cartage of refuse to a tip than
to a destructor. By letting the electricity department bear the cost of
destroying the refuse, and returning the clinker to the sanitary depart-
ment, that department was benefited while the steam generated was
doing good to the electricity department. There was now no difficulty
in regard to combined destructor and electric stations. They had got
now to such a state of efficiency that it was easy to get guarantees of
40 k.w. per ton of refuse with good engines and dynamos. He had
obtained more, but he had no difficulty in getting 40 k.w. per ton if the
plant was carefully designed and the whole arrangements carried out
on proper engineering lines. He preferred where he put down a
destructor station to have a storage battery. It was advisable to
destroy the refuse without loss of time and then to store up the
energy.

Regarding gas-driven stations undoubtedly there was a field open
in this direction, especially where the Council owned its own gas works,
but his experience was that the author had somewhat underrated his
gas consumption, for to run as he proposed twenty hours out of twenty-
four with little or no load, his engine would be running very light,
while all the time it was taking gas to drive it, and considering that
even with vertical gas engines of the most modern t5rpe they could
only get a guaranteed mechanical efficiency of about 85 to 86J per
cent, (he could not get any more, depending on the amount of load),
if the engine were running for twenty hours, there must be a considerable
amount of gas simply running the engine, which would increase the
cost per unit for the time during which current was supplied. He had,
some time ^ince, got out the return for eight months of a gas-engine
station as follows : —

The average gas consumed, current being measured at the switch-
board, worked out at 64 cb. ft. per unit. The engines were by a

1903.] SMALL TOWNS AND VILLAGES: DISCUSSION. 1027

leading maker, chloride storage battery, 3,500 lamps on the mains, ^J;,^^^
but practically no day load.

The gas cost 2S. gd. per 1000 cb. ft, therefore it worked out at
2*2d. This was a rather large consumption of gas, but the efficiency
of the dynamo was not very high, and there was the loss in storage.
He had tried another place, and took a 30 B.H.P engine, and that
worked out at an average of 35 cb. ft of gas per unit. Another test
of a smaller engine, 16 B.H.P., at the same place, gave 34 cb. ft. per
unit. He could not say why the smaller engine should have come out
more efficient than the larger one, but he found that the large engine
had got an excessively heavy fly-wheel on one side only, and also a
large fly-wheel on the dynamo an^ a very long drive. It was said that
fly-wheels did not take any driving, but this proved the contrary.

As to the advisability of putting in a battery where there was a gas
plant, a battery was required in order to save running the engine with
no load. It paid to have a 30 per cent, loss in the battery, together
with interest and sinking fund charges, rather than to keep the engine
running night and day. Moreover if the engine were of the " hit and
miss " type the battery was almost a necessity.

Gas companies being under no obligation to supply gas for power
purposes, but only for lighting, the thermal efficiency varied consider-
ably, and the speaker had found it as low as 400 B.Th.U. per cb. ft
At Hebden Bridge they were putting down a gas-driven station on
lines which he believed were quite new. The Council owned the gas
works, having bought out the local gas company, and among the plant
was a Glasgow and Humphrey water-gas plant, which cost about
;g5,ooo, but with the present comparatively low price of coal and for
other reasons this plant was practically idle, and in order to provide
work for it, the question of power gas had been carefully considered.
The Mond plant was found too expensive for a small place, as other
gas plants would do the work cheaply and satisfactorily. In order to
settle practically the utility of the Glasgow- Humphrey plant a gas
engine had been put down and run at different loads up to 48 B.H.P.,
the carburetting process of the plant not being used, as the cost of the -
oil would bring the cost of gas beyond that of gas produced by other
water-gas plants in the market and therefore the plant was used purely
as a water-gas generator.

The result of experiments extending over some three weeks had
resulted in the Council deciding to utilise the plant. The tests were
most carefully made, the engine being braked on the fly-wheel in the
usual manner and indicated at the same time. The gas was metered
into the engine and the thermal efficiency of the gas regularly measured
by a Junker's calorimeter and reduced to standard temperature and
pressure, the coke was weighed into the producer and the gas passed
into a large holder. Briefly, the result was as follows : The gas
committee had arranged to sell and deliver the gas to the electricity
department at 6d. per 1,000 cb. ft., which left a good profit to the gas
committee. Guarantees had been obtained from the engine builders
to give one kw.-hr. per 60 cb. ft. of gas, the thermal efficiency of which
averaged 244 B.Th.U. per cb. ft The engines were of the four-

1028 MOUNTAIN: ELECTRICITY SUPPLY FOR [Leeds,

Mr. cylinder type, 250 B.H.P. direct-coupled, and to run at 250 R.P.M.

Emmott ^g ^j^g g^ ^^^^ somewhat richer in hydrogen than some of the producer
gases, the piston as well as the cyclinder had to be water-cooled to
prevent heating and pre-ignition.

As to Mr. Mountain's suggestion, he should be a little nervous about
leaving a plant to take care of itself all night, and was afraid it would
often be awkward if the consumer had no other illuminant to fall back
upon.

As to overhead wires. In very small places overhead wires might
be put in, but in his experience they were not entirely satisfactory. He
• had run from August, 1890, to 1893 with overhead wires, in Halifax, at
a pressure of no volts for the central part of the town and for the
outer area at 1,200 volts transforme'd down to no. These overhead
wires were a continual source of anxiety and the upkeep was more
than that in underground work. He would prefer to see how he could
reduce other costs, and lay the wires underground. He would not go
to the expense of putting down troughing, but would run the risk (if
any) of putting down lead-covered armoured cables. The cost of
opening out and filling in the ground and making good pavements in
country places was not so serious as in a place like Huddersfield. The
roads could be opened out and filled in for about is. per yard.

He ran the National Electric Supply Company's Preston lighting
for about twelve months overground on pitch-pine poles, but was glad
when they had to be taken down. The engines were of the semi-
portable type, suggested by Mr. Mountain, and were made by Marshalls,
of Gainsborough. They were very satisfactory, but the coal bill was

Mr. ^»g^-

Wilkinson. Mr. G. WILKINSON Said that the supplying of small towns opened

up a very large field, the fringe of which had hardly yet been touched.
A scheme might be prepared for a small area and presented in the best
manner, but the authorities nearly always turned round and asked
where a similar one was to be seen ; and it was natural that any Town
Council should hesitate until they could see something like the one
proposed. This he thought largely accounted for difficulties i and 4.
The principal reason that had delayed lighting was the visionary one
that District Councils had as to the grand time that was coming when
the Power Companies would be able to give them power practically for
nothing.

It was his duty not very long ago to approach the Yorkshire Power
Company on behalf of a District Council with regard to terms of supply.
They asked for a minimum supply of 25,000 units at 3^. per unit ;
from 28,000 to 125,000 at 3Jd. Up to 187,500 at 3d. (It would be a
rather large village which would take that.) Up to 250,000 2jd., and
over that 2jd. per unit delivered. To these must be added losses in
distribution.

In reply to a question by Mr. Mountain as to what they would do
with the supply the speaker said that they (the Power Company) pro-
posed to supply at a given fixed point at this rate, and as a concession
the District Council was to take the bulk of the energy and deal with it
as they pleased. He found that to this item must be added £8,500 to

1903] SMALL TOWNS AND VILLAGES: DISCUSSION. 1029

;^Q,ooo in putting down mains, house services, meters, buildings, etc. Mr-
An engineer and manager would have to be engaged, and all the risk of
bad debts and the like would have to be taken, and in fact, except for
the stoking of boilers, the entire business of supply would have to be
undertaken. In the case of villages the whole of the capital outlay must
be most carefully spent ; there was no margin to work upon, as was the
case in a large area where the lighting density was fairly heavy.

He did not think that the future lay with destructors, unless there
was a strong reason from a sanitary point of view, as the initial outlay
was very large indeed, and the advantages did not warrant it. He
thought the refuse should be put on the land rather than burnt, as
there was in many of these areas plenty of tipping ground.

It was difficult to say what form the combustion engine would
eventually take, but he did not think steam had any chance. He
thought there was something to say in favour of oil and town-gas rather
than producer-gas and steam. In the paper, lo lbs. of slack per unit at
8s. a ton was mentioned, but he did not think that there were many
places where it could be obtained at that price, as there are many
villages where cartage would cost you 2s. 6d. per ton. Regarding
town-gas figures, the price was put down at 2s. per i,ooo cubic feet.
In Harrogate the least it could be obtained at was 3s. 2d., less 10 per
cent. ; in Otley it was 3s. 4d. ; Wells was 5s. 3d. and Tadcaster 5s. 3d. ;
and he, therefore, thought that this figure should be increased ver}'
considerably. Again with regard to combustion engines he said that he
knew one of the big supply companies was just concluding a contract
for a 1,000-kilowatt internal combustion engine rather than increase
their boiler and steam plant.

As to oil-engines. Oil was given at o'5d. per unit, but he thought
it could be done for very much less. He should be inclined to put it
down at 023 to o-25d. Another point with regard to the 4 H.P. plant to
be used instead of accumulators. His opinion was that it would not be
safe to allow it to take care of itself entirely. Up to a few months ago
he produced his own electricity at home by a 3J kilowatt dynamo
driven by a Paris-Singer gas engine. Accumulators were not used, and
the cost of running did not exceed the cost of lighting by gas.
Accumulators need not be very expensive, and would be a safer
arrangement, the station could be shut down entirely for daylight hours,
and they would give an economical load while such plant was running,
and he would very much prefer to use them.

Mr. Mountain said " the estimated lamps connected during the first
two years are 3,000 of 8 c.p. . . . and the first instalment of plant would
therefore require to be equal to about 60 kilowatts.'' It did not appear
from this that any spare plant was provided, and he would be glad of
further information because it was always understood that a certain
amount of stand-by was an absolute necessity, and he therefore
thought that the capital outlay would have to be increased for this
stand-by plant.

He quite agreed with Mr. Mountain as to the future of overhead
rather than underground distribution for thinly populated areas, as it
was very much easier to look after the distribution of overhead than

1080

MOUNTAIN: ELECTRICITY SUPPLY FOR

[Leeds,

Mr.

Willdnaon.

Mr. Harris.

Mr.
McLachlan.

underground cables, and there were no expensive joint boxes as in an
underground system.

Mr. Harris said that towns' refuse was now being largely employed
in the production of electricity at a cheaper rate than any other method
in existence where fuel wa§ to be used, and the consulting engineers in
general were now recognising this fact Professor Kennedy, for
instance, had at the present time 4 or 5 stations where he was recom-
mending a refuse destructor because of its cheapness. From a sanitary
point of view the refuse should always be destroyed, and corporations
and councils had come to the conclusion that a destructor was necessary
and that they might just as well have a return for the cost of the outlay
in the production of electricity. This was an important factor in
determining the electric light stations being put down at Cleckheaton
and Shipley. He was of opinion that it would pay all towns, and small
towns in particular, to take up the subject and bear the whole cost of
putting down the refuse destructors in connection with electric light
stations.

He gave a comparison between the cost of generation by coal and
by refuse. Taking an average cost of fuel and wages, and allowing in
each case only one man for the boilers, he showed that the difference
was very great indeed. Taking a yearly output of 87,000 units the
average price per unit (taken from the Electrical Times) was i*353d.
With a refuse destructor, including interest, sinking fund and repairs,
it was o'376d. Again, with a coal plant, between 87,000 and 131,000
units per annum, the cost was i*053d., while with a refuse destructor
plant it was 0*391 d.

The engine-room charges and interest on the electric light station
were left out. Taking again a larger plant of 131,000 to 175,000 units,
the cost for coal, firing, and one man was o'939d. as against a destructor
station o*295d., and coming to a still larger one of 350,000 units coal,
firing, and one man o*9i6d. as against refuse destructor o'264d. It was
certain that only the largest stations in the country were producing
electricity with a fuel cost of anything like o*26d. The figures would
allow for ample margin for interest and sinking fund charges, and the
working results in different places confirmed these figures.

At Darwen for the last financial year the refuse destructor effected
a saving equal to £1,050 in coal, although they were working non-
condensing, and if they had had an economiser the saving would have
been very much greater. It was quite the usual thing to get 40 units
per ton of refuse, and in some cases over 60 units, and he expected to
hear of still more. He thought that it would pay station engineers
generally to push the subject more than they are doing, and advocate
the use of town refuse instead of coal.

Mr. McLachlan said that there seemed to be some misunder-
standing with regard to the cost of gas in small villages. It was
produced in York for is. lod. per 1,000 cb. ft., whereas it was quoted as
at 3s. 2d. in Harrogate and 5s. 3d. in Tadcaster. If an agreement were
made with the gas company it was probable that it could be obtained
at from 8d. to is., which reduces Mr. Mountain's figures by 50 per cent.
With regard to producer-gas, Mr. Mountain was on the right side, as

1903.] SMALL TOWNS AND VILLAGES : DISCUSSION.

1031

guarantees could be obtained to produce a unit for 2 lbs. of coke, as
against the 3 lbs. given in the paper ; and, again, coke could be obtained-
at from 8s. to los. per ton from many gas companies, as against the i6s.
given in the paper, and this still further reduced the cost. He thought
that the repairs might have been brought down a little more. If all
these things were reckoned together it would be seen that electricity
could be produced for about 2d. per unit, which was a saving of nearly
one-third. The figures given by Mr. Emmott, viz., 64 cubic feet per
Board of Trade unit, were rather peculiar, because any good type of
gas engine could now be reckoned to consume something less than half
of that. Passing on to the question of power he said that nobody
seemed to have thought of the fact that electricity could be used for
power in small villages, although not to any large extent.

Mr. M. B. Field said that he could not agree with Mr. Mountain
that the total cost per unit would come out at 3 •83d., and that there
would be a good profit at 4Jd. with a plant of the size contemplated by
him. The question as to whether it was going to pay to supply small
villages from a large power station depended on many things, amongst
others, on the size of the village, and the amount of power required ;
also upon whether power could be conveniently tapped ofiF from a line
arranged to supply, say, a very much larger village somewhere else.
The question was largely determined by the matter of overhead lines or
underground cables, and he did not see why there should be any
uneasiness whatever with regard to the former.

They were universally adopted in the United States and Canada
and on the Continent, and he thought that when the Board of Trade
had sufficiently advanced to allow them that there would be a far better
chance of supplying small towns and villages from the large power
stations at a comparatively cheap rate.

In regard to the objection of Mr. Mountain to the large power
schemes on the ground that buildings would be necessary and
machinery would have to be erected, attendance provided, etc., he
could only say that in America lines were run for many miles and
absolutely no attendants were provided for at the far end for carrying
out the transformation or distribution of the energy.

Mr. E. A. Paris said that as one of the oldest missionaries he had
passed through the various phases of the several controversies — con-
tinuous-current versus alternating-current, accumulators versus running
plant, and large central stations against small isolated plant — and he
was certain that the small isolated plant with a highly efficient prime
mover would win the day.

He thought that the oil-engine had a very great future before it,
more especially for the kind of lighting treated of by Mr. Mountain.
He agreed with the author as to the senseless opposition of many local
authorities, who obtained a provisional order and then did nothing
until some effort was made to start a company.

Mr. S. D. ScHOFiELD said that he considered Mr. Mountain had
taken some very low costs, ^ there were many stations even in the
coalfields where the coal cost exceeds o*42d. per unit. If stations with
from 500 to 800 kilowatts installed could not get below o'6, and in some

Mr.

McLachlan.

Mr. Field.

Mr. Paris.

Mr.
Schoficld.

1032

MOUNTAIN: ELECTRICITY SUPPLY FOR

[Leeds,

Mr.

Schofield.

Mr.
Wallace.

Mr.
Broadbent.

Mr. Brook.

cases o'8 or 09, how could a country village he expected to ^^et to 0*42
or anything below o*5d. ? In some cases it would be more economical
for a private company to start a supply in a village without obtaining a
provisional order, as they would be in a better position owing to there
being no restrictions against overhead conductors. The success or
otherwise of a small station, quite as much as the success of a large one,
depended upon the esprit de corps of the staff. He thought that the
engineer that would make a small place successful would be one that
was always out canvassing and who would act as consulting engineer
for the wiring of installations and would advise upon the installing of
motors in order to help to get a motor load.

Mr. G. S. Wallace said that before wires were erected permission
would be necessary to carry them over property, although, of course, if
the District Council were doing the work the difficulties would not be
so great on the main roads, but they would still have some difficulty in
going over private property, and with a private company this would be
more noticeable and would increase their annual charges very con-
siderably. Again, he thought that there would be a great fear of the
wires, as the demand increased, becoming very unsightly, and that in
consequence objections would be raised, which would in many places
lead to their being removed. He was surprised to see that the repairs
in each case were taken at o'i6d. per unit, as he was sure that, if the
underground system were properly laid, the repairs should not be so
high as for the overhead system. He noticed that the cost for depre-
ciation for underground cables was o'69d., whereas for the overhead it
was o*4d. Seeing that poles had to be taken down and possibly erected
elsewhere and that, they required renewing at certain intervals, he
thought that the depreciation would be greater with overhead cables.
If there were at all sufficient margin to allow for underground cables
in the initial arrangements of the plant he should certainly recommend
them rather than aerial wires, because when a good supply was obtained
the aerial cables would have to be replaced by underground conductors.

Mr. Broadbent said that he had a small private plant in which the
cost of production in gas came out at 075 per unit, but the accumu-
lator depreciation brought it up considerably. He supplied energy
to friends at 6d. per unit and charged them 15 per cent, per annum on
the cost of mains. He found that it was best to run his gas plant at
the full output and use accumulators.

Mr. Brook said he could speak with actual experience as to the
reasonable figures given by Mr. Mountain. He gave some particulars
of a gas-driven plant put down by him at Brighousc. Over 4,000
8 c.p. lamps were connected to the mains and 84 brake h.p. was
installed and a storage battery was also used. The revenue from the
sale of current was about £550 a year, which works out at about is. 9d.
per lamp. The units sold were 23,000, which could be increased by
applying a little encouragement. Current was charged for at the rate
per unit of 6d. for lighting and 5d. for power. Owing to the fact that
insufficient plant was installed to take the maximum load the battery
had to take a large share of the supply, and the cost per unit supplied
was fairly high. Gas was charged at 2s. 9d. per 1,000 cb. ft. from

1903.] SMALL TOWNS AND VILLAGES : DISCUSSION. 1033

the town mains. He thought that the power companies would find a Mr. Brook,
great difficulty in supplying most of the small towns and villages. He
thought that the item for repairs in the four cas'^s given was rather
high and should be brought down to one-half. With regard to over-
head wires, during the whole six years that he had charge of the
Brighouse plant they required no supervision whatever, and he never
had any breakdown owing to the failure on their account.

Mr. A. L. C. Fell drew attention to a rather misleading point on Mr. Fdi.
page ioi8,in which it was stated that public companies would supply at
2i<i. per unit, whereas it could be generated (it was said) for Jd. or id.
On page 102 1 it was shown that at the very best it could only be produced
for 2'9d., and he did not see how these figures agreed with one another.
Again Mr. Mountain stated that in a case of a tramway undertaking
the revenue commenced at once, whereas the revenue from an electric
supply undertaking could only grow gradually, but he did not think
that this was quite correct, as, for instance, in Sheffield the revenue had
gone up considerably with the same number of cars running.

With regard to the question of steam generation he thought ten
pounds of slack per unit a great deal too high, as five or six pounds per
unit was quite sufficient ; and, again, slack could be obtained for some-
thing like 6s. per ton, as against the 8s. given in the paper.

He did not see any reason why the Board of Trade should not
consent in the case of a small village to do away with the present
regulation to the effect that the plant should have to run all night, as
ae thought it could be shut down at eleven or twelve o'clock, and if
this could be done there would be a chance of running the plant at a
considerably lower cost. He thought that the local authorities did not
take up the question of supply because of the misleading statements
which were made about the large power companies, and they did not
trouble to inquire as to whether they could not supply themselves
more cheaply.

Mr. Baker (communicated) thought that the author's proposal to Mr. Baker,
work a small plant all night without attention was a bold stroke, but at
the same time it was warranted by experience. He himself had fre-
quently, in a small private plant, left the engine working all night
charging accumulators, and he did not remember that on any single
occasion was there any trouble.

He differed materially from Mr. Mountain concerning the value of
electric power supply companies, as electricity supply became a simple
matter for a local authority when the generating works were dispensed
with and the problem was simply that of purchasing in bulk and
retailing at a profit.

In the paper attention was directed to the employment of motor-
generators, but a large volume of the business of the power supply
companies would be done through stationary transformers supplying
alternating current. He thought there would he a reduction in the
cost of the distributing mains owing to the central position in which
such a transforming chamber could be located. Again it might
frequently be practicable to use one generating station for several
small towns close together.

1034 MOUNTAIN : ELECTRICITY SUPPLY FOR - [Leeds,

Mr. Baker. He thought the author was right in eschewing condensers in con-

nection with small steam generating plant, unless there happened to
be an available stream of water sufficient to work an ejector con-
denser. The use of a destructor would very materially increase the
capital cost in a small system, and a reasonably large accumulator must
be added. The most suitable towns for the combination of refuse-
destructors and electrical works were those having from 10,000 to
30,000 inhabitants, the limiting number being a sufficient population to
provide refuse, and on the other hand a population whose demands are
within the range of an accumulator, of which the prime cost was a
determining factor. He thought it would be difficult to find an
example of 30,000 units per annum being generated at a total cost
of 2'59d. per unit, though the figure might be obtained.

Some slight advantage was obtained by pushing the supply voltage
as high as possible, particularly when accumulators were not employed,
and he thought that the 200 to 220 volts should be made 230 or 240
volts at the consumers' terminals.

Mr. Cruise. Mr. E. G. Cruise (communicated) wrote that the question was of

undoubted importance at the present time to electrical engineers,
companies, local authorities, and to the industry generally, as the list
of large and important towns in the United Kingdom where a supply
of electricity had not been already inaugurated or arranged for was
fast becoming exhausted. It was, however, somewhat alarming for
the financial outlook of the electric power companies to read the
confirmed opinion of the author and many of the engineers joining in
the discussion that these companies would have no field whatever for
their work of bulk supply amongst the small towns and villages.
When these power schemes were before Parliament for the first time
in 1900, the evidence submitted to the special committee which first
sat to deal with the schemes was largely directed to show that only by
the sanction of these power companies could the small towns ever
hope to obtain a supply of electricity at a rate profitable to consumers.
Parliament was impressed with this argument and the evidence which
supported it ; it destroyed the opposition evidence, and there was little
doubt but that it was in large measure responsible for the passing of
the Pioneer Act, the County of Durham Power Scheme. The prece-
dent once set, the subsequent Acts were more easily obtained, and the
evidence referred to was repeatedly quoted in the progress through
both Houses of the multitude of Power Acts which had now become
law. The special committee above mentioned consisted of eight
instead of the usual four members, and had been chosen to include
some of the best known business men and financial experts of the day,
so that due weight must be given to their judgment regarding the
schemes. For the purely engineering evidence they were, of course,
necessarily in the hands of the electrical engineers who gave evidence.
The underlying principles, however, of the Power Acts were in such
large nieasure principles of financial economics, that it may be taken
that their passing by Parliament was tantamount to conviction as to-
their benefit to electricity consumers in the lesser towns and in
outlying villages.

1903.] SMALL TOWNS AND VILLAGES: DISCUSSION. 1085

He had no doubt that the evidence before the committee was also Mr. Cruise,
well known to Mr. Mountain, but he had perhaps lost sight of the fact
that the present rates offered by the power companies were in no
sense indicative of the ultimate rates which they would be able to
o£Fer. Obviously so long as their load-factor was not vastly more
favourable than that of the local supply station, they must commence
by rates which would secure them against working at a loss. Even
with these initial rates, however, there would seem little room for
doubt that they would be widely accepted by the authorities proposing
to distribute in the small towns and villages. One point, however, to
which Mr. Mountain very rightly referred was the absolute necessity
of obtaining sanction from the Board of Trade to having overhead
transmission lines, and if this applied to the local distribution, assuredly
it applied with double force to the trunk lines of the power companies.
This would seem a point to which the power companies had not, so
far, given sufficient attention. The explanation might lie in the fact
that cable companies were largely interested in the power companies.
Agitation on the subject had been developing lately, and even in 1900
a special committee of the London Chamber of Commerce had been
appointed to approach the Board of Trade on this subject, and a full
report deaUng with the question of overhead wires and other questions
regarding the economic aspects of the carrying out of the Power
Acts, was issued by the Committee. So far no general concessions
had been made, but the Board of Trade was undoubtedly now more
disposed to deal favourably with the question of overhead transmis-
mission, a system in universal use except in the United Kingdom. . He
ventured to think that the wholesale laying of underground power
cables in these schemes at costs of and above £it(xx> per mile per
1,000 k.w. cable would wholly defeat the ends and destroy the
financial success of the power companies.

But whether the power companies prospered or not, or whether
they offered rates far below those obtainable from isolated stations,
there was no doubt that there would always remain small and trucu-
lent towns where the local authority, or even perhaps a company,
would insist on putting down their own generating plant, and it would
be in the consideration of such cases that Mr. Mountain's paper would
have immediate appHcation. Further than this, there would be many
such towns where power companies would have no trunk mains for
years yet, if ever, and such places would require a pioneer or perma-
nent isolated plant.

Regarding, therefore, the actual questions arising out of the paper,
he ventured to suggest a few points. From personal experience cf an
Inquiry held recently by the Local Government Board for a loan of
£6jcxx> for electricity works in a very small town of 4,000 inhabitants,
he was able to say that in such cases the Local Government Board
would probably not consent to a sinking fund for repayment of the
loan. In the particular case in question they absolutely refused to
sanction any other scheme of repayment of the loan than the yearly
repayment in cash of the total sum of the loan divided by the number
of years it was to run. Thus, the best terms obtainable being a period

1036 MOUNTAIN: ELECTRICITY SUPPLY KOft [Leeds,

Mr. Cruise, of twcnty-five years, it was evident that an initial annual charge of 4 per
cent, on the capital of the undertaking must be allowed for as against
the figure of 2J per cent, submitted by Mr. Mountain. Taking interest
at 3 J per cent, we arrive at a total of yi per cent., thus leaving prac-
tically nothing for depreciation in Mr. Mountain's tables, and the Local
Government Board are very exacting in the case of small schemes for
some prospect of such provision. To meet the case, therefore, under
the circumstances the price must be raised above the figures given in
the tables.

Regarding more especially the producer-gas figures, it was very
doubtful whether for such small plants as those in question manu-
facturers would give any satisfactory guarantee as to the quality and
continuity of the gas generated if coke alone were used. The figure
of 3 lbs. of coke per unit sold seemed altogether too low, seeing that
in the case of Walthamstow a very successful and typical producer-
gas station, where the sets were 75 k.w. output each, and best pea-nut
Anthracite coal was used, that the figure per unit sold was about
3*2 lbs. of fuel. In the case of really small towns and the proposal to
use town gas where available, it would seem that the figure of 2S.
per 1,000 c. ft. is too favourable. This in many cases would un-
doubtedly be below the cost price of making the gas. In the town
above referred to the price was about 5s. for any purpose, and this
would appear to be a not uncommon figure in very small towns. In
such cases town gas was out of the question. Regarding the overhead
distribution wires, the Board of Trade would only so far give a
provisional sanction for five years, and this not in all cases, and
apparently if wooden poles were proposed, the Local Government
Board might shorten the period of the loan. The proposal to have an
all-night running of the plant with a small set was a novel and in-
teresting one, but it appeared to be very desirable, especially in a
small station, to have a small battery at least, to give the necessary
light in case of a breakdown. Such accidents would happen to small
plants, and the difficulty was largely increased if no good source of
light were available for immediate inspection of the various parts of
the plant.
IIP Mr. A. B. Mountain said that he would reply to the points in the

Mountain, paper as they occurred, and not to the individual speakers. Taking
first the considerations that appealed to the influential people, the
difficulty was that one must somehow persuade the people who live in
the district that one can give them a supply at such a cheap rate
that they would adopt it, and that the undertaking would be financially
successful.

In large cities like Leeds, with all its conveniences, he did not think
they appreciated the backwardness of the small places. There were
thousands of places in England where there were no street lamps, and
no effort whatever was made to light the houses, and in those places
small plant could be put down and run at an exceedingly low rate.
In a country place a small gas engine could be put down and allowed
to run alone all night to supply, say, 50 lights, which was all that would
be required. Engine lubrication was now so perfect that there was not

1903.] SMALL TOWNS AND VILLAGES: DISCUSSION. 1037

the slightest difficulty in letting them run by themselves for 12 hours. Mr-
Mr. Field put the case for the power companies, and, assuming that
the power companies could supply the works here at a cheaper rate
than the works could provide power themselves, Mr. Field was no
doubt right, but an examination of figures showed that the cost of
producing energy in mills was only something like o'2d. to o'3d. per
unit. It seemed impossible for any power company to persuade the
owner of that works to scrap his steam plant, and put in motors, and
take the supply from them, even if they could come to that price, and
Mr. Field would agree that it must be many years before they could
supply at a price anything like that. Further with regard to power
companies, he said that the distributing authority must have some
central point or have sub-stations for distributing, and to which the
power companies would bring their supply, thus leaving the District
Council with the whole of the cost of the distributing services, and
mains and other items, including management. He did not think that
there was the slightest possibility of the power companies ever help-
ing in any way in the supply for small places.

With regard to the criticism of the figures, he thought that he had
not under-rated the amount which would be required to run the
works ; the figures were taken from certain engineers who had gas-
plants under their control. It was quite possible that the average
figure would be slightly higher than 25 cb. ft. per unit. If the figure
was altered from 25 to 30 cb. ft. per unit and the price of gas reduced
6d. he would be on the right side, and eighteenpence per thousand
was quite high enough.

Mr. Emmott was very severe on the question of overhead wires,
but if he were given the opportunity of pushing electricity he (the
speaker) thought that he would agree with him that id, or id. per unit
in the cost made all the difference between a scheme succeeding and
faiHng, as the question of cost in a small place was far more serious
than in a large place. In a small place the working-class had to be
supplied, and therefore the very cheapest system must be used, and he
was convinced that if we went in more for overhead wiring we should
find the simplest way of getting over the difficulties. He found that
the repairs themselves to underground mains were not expensive, but
when the cost of taking up the roads and also of interference with the
traffic was considered, the item was a very serious one.

In the case of overhead wires put up firmly on poles, repairs could
be undertaken by anybody without specially skilled knowledge, and
they were easily accessible in <^se of a fault occurring, whereas in the
case of underground mains, there was trouble with the District Council
if it was a private company, and friction between the various depart-
ments if it was a Corporation.

If destructors were adopted, the first thing to do was to encourage
in every possible way the adoption of electricity for motive power
purposes.

Mr. Emmott mentioned small batteries, but if there was one thing
an engineer must fight against, it was the employment of small batteries,
and with batteries there must be some one who really understands

Vol. 82. 69

Mountain.

1038 MOUNTAIN: ELECTRICITY SUPPLY. [Leeds,

Mr what he is doing, as there are more batteries destroyed from want of

knowledge than probably anything else, and he was therefore suggest-
ing the employment of small engines to replace batteries, and he felt
certain it would reduce the costs considerably.

Mr. Fell has drawn attention to the statement that the cost of
production would be id. or id. as against 2^6. if purchased from a
power company, and then points out that the cost of production as
shown in my paper is 2'9d. This figure includes management, depre-
ciation and financial charges, all of which will require adding to the
2jd. paid for the energy.

Mr. Cruise has stated the case for the power companies very
forcibly, but beyond obtaining powers these companies appear to have
made very little progress, although they have effectually stopped the
introduction of electricity into the small towns and villages which are
now reconsidering the matter, and are likely to do so for many years,
thus blocking progress.

It does not matter to a local authority whether the capital is repaid
by annual instalments or by means of a sinking fund, the total amount
to be provided annually is practically the same.

1903.] BRUHL : PRESERVATION' AND PACKING OF PLANT. 1039

CALCUTTA LOCAL SECTION.

ON THE PRESERVATION AND PACKING OF
PLANT FOR AND IN BENGAL.

By Paul BrDhl, Member.

{Abstract of a Paper read at Meeting of Section^ March 27, 1903.)

After an experience of over twenty years in the " care of plant in
hot and moist climates/* the author refers to the nature of the adverse
climatic influences which have to be combated by those in charge of
laboratories or central stations, as being mechanical, physical, chemical,
and biological.

In the "mechanical" he includes the subject of packing and care in
transportation. He regards some conditions in respect to handling of
cases containing scientific instruments as unalterable. As regards
design he says : —

** Ample and efficient provision should always be made for securing
the coils of suspended-coil galvanometers, the magnetic systems of
Kelvin and Helmholtz galvanometers, and other loose or oscillating
parts of instruments. There is absolutely no sense in the manufacturers
fitting on the suspension, and not taking precautions to prevent the sus-
pensions getting broken, before the instruments reach their destination.
An ideal which designers ought to keep steadily before their mind's eye
is one which Clark Fisher refers to in his book on the potentiometer :
an instrument should be so designed that, provided it is properly
packed, it should be possible "to throw it across the room with
impunity or even to send it by rail in the United States." Portability
and security during transit is a condition which most instruments sent
out to this country ought to satisfy.

"In machines, sections which give rise to injurious stresses after
casting, or such as create lines of weakness along which concussion is
likely or certain to produce fracture should be carefully avoided, and
pins or bolts or screws which hold parts in position should be designed
of a sufficient cross-section to prevent shearing taking place. Some
time ago I received an electric motor with the insulation of the wires
on one of the end faces of the armature scraped off and the wires
partly cut into by some part of the frame. The cause of the mischief
lay in a pin which had the function of keeping one of the shaft bearings
in position having been sheared right through, probably in consequence
of the case containing the motor having been dropped from a railway
waggon or into a ship's hold ; and a trifling difference in the design of
the bearing would have prevented the accident. It would be a good
thing if every designer of instruments and machines manufactured for
export made himself intimately acquainted with the special conditions

1040 BRUHL : ON THE PRESERVATION AND PACKING [Calcutta,

of transport. Personally I believe that, with proper design and proper
packing, accidents to instruments need hardly ever occur except in the
case of a railway collision."

On the subject of packing — which is an engineering one, and of
moment as affecting successful exportation — he says : —

" Most of the larger firms of manufacturers of physical and chemical
apparatus have evolved, on the basis of their own and other people's
sad experiences, methods of packing which in the majority of cases
prove fairly efficient. Of late years I have only rarely received articles
in a broken condition ; but then I make it a point to deal only with
first-class firms. Very effective is a description of wood shavings, con-
sisting of very thin, very long, and very narrow strips which seem to be
specially manufactured for the purposes of the packer.

** It is self-evident that parts should never be lying loose in their box.
One of the worse sins of commission on the part of a packer is to pack
very heavy and bulky articles in the same case with delicate parts ; and
yet that is done again and again, as if the packer considered the heavy
parts to be specially designed to triturate the delicate parts into a fine
powder. All heavier parts should be tightly fastened down by screwed-
on battens ; and if it is found unavoidable to p:*ck smaller articles in
the same case with larger and heavier ones, they should be packed in
Separate small boxes. All this seems simple ani} self-evident; but
unfortunately sufficient attention is not always paicNJo these details,
and it is astonishing what thoughtless blunders are j^metimes per-
petrated by the packer.'' \

On the subject of temperature he says : — \

"It does not appear to me that the higher tempera wres of the
tropics and sub-tropics, taken by themselves, play a very\ iropo^^^
part\in connection with our subject. It is doubtful whether any
dynamo has ever been injured by being run under full load,\ although
the starting temperature of armature and field-coils has been s*y lo^ or
even no degrees Fahrenheit, and therefore 20 or 30 degree* higher
than the initial temperature would be in England. There arf only a
few instances known to me of the higher Indian temperatures Ipausing
temporary or permanent trouble. One case occurred with one (P^ ^^^
Kelvin's current balances, in which, during the first hot weatljier the
coils commenced to sweat out some of their paraffin, causing thtt n^^^^"
able coils to stick. A small quantity of the more fusible paraffin Shaving
oozed out, the remainder having a higher point of fusion renJained
behind in the solid state, and the balance has been in first-class woc^^lS
order ever since. But it is advisable for manufacturers of apparatus in
which paraffin is used for insulating certain parts, to use only paija^"
of high melting points in apparatus meant to be used in trojjP^^
countries. f

"It is possible that the higher temperatures of the tropics ^'^f^^
something to do with the dust which may happen to lie for some/*^*™^
on varnished parts of apparatus becoming ingrained in the c-*^^^ ^^
varnish and spoiling its appearance for good. The only ren^'^^y *"
this case is frequent dusting and keeping the apparatus unde: ^ cover
when not in Ubc."

1903.] OF PLANT FOR AND IN BENGAL. 1041

The effect of high temperatures on chemical agents is discussed as
follows ; —

** It is different with higher temperatures acting in conjunction with
chemical agents ; in this case the influence of temperature ceases to be
negligibly small. It is well known that the time-rates at which chemical
actions proceed are not only generally speaking functions of the tem-
peratures at which they happen to take place, but they are often rapidly
increasing functions of the temperatures and are therefore frequently
represented by curves which at first are nearly horizontal, but beyond
a certain point curve rapidly upwards. Unfortunately hardly any
precise data are available on the relation between temperatures and
the time-rates at which such chemical actions take place as the rusting
of iron, the formation of verdigris, the action of nitre on various sub-
stances interesting to the electrical engineer, the chemical changes
which lubricating oil and allied substances undergo in contact with
the atmosphere, the action of carbonic acid on various silicates, the
action of atmospheric ozone."

The rapid rusting effects in the rainy season are not much prevented
by the process of "blueing." For instruments the author has used
Vacuum Company's spindle oil laid by means of a brush as a protecting
covering. The use of this on the steel parts of exported instruments,
the oil being first carefully tested for the presence of acid, he strongly
recommends. He recommends that all swinging parts of fine balances
and accurate sets of brass weights should be platinised. He objects
to gilding ; he prefers phosphor bronze to steel where suitable, and in
balances, used in electrolytic work, knife-edges should be of agate.

" Aluminium, provided it is pure, appears to stand the tropical climate
tolerably well ; some aluminium, however, becomes quickly converted
into hydroxide, and on the whole I do not advise the use of aluminium
for parts of instruments ; of course where special lightness is required,
the use of aluminium may be unavoidable. There is little trouble with
German silver and platinoid. Stretched Iridium-silver wire, as some-
times used in meter bridges, invariably snaps. Bare manganin is not
quite climate-proof and requires careful watching. A peculiar change
takes place in the suspension strips of the D' Arson val galvanometers of
some makers. After a short time one finds the resistance of the galva-
nometer to increase rapidly, until it nearly reaches infinity. On exami-
nation one finds the strip converted into an exceedingly fragile thread
of oxidation products."

Another marked source of trouble are galvanometer mirrors. He*
says, " I have repeatedly received galvanometers with the silvering of
their mirrors either cracked all over and portions of it flaked oflF or
rendered useless by tarnishing. As the best temperatures for silvering
such mirrors lie about 20° centigrade, the temperatures ruling in India
are usually too high for an attempt to re-silver one's mirrors one's self
to prove an unqualified success.

" One of the most powerful corroding agents employed by nature is
carbonic acid. We are accustomed to look at carbonic acid as a weak
acid ; at least, that is what elementary books on chemistry tell us. Of
course, it is weaker than various other acids ; but in many instances it

1042 BRUHL: ON THE PRESERVATION AND PACKING [Calcutta,

is weak only because it is volatile — volatility is not usually compatible
with strength—or, it is weak because in an aqueous solution prepared
under atmospheric pressure it is exceedingly dilute. But when the
acid is more concentrated under the action of high pressures, the effect
is markedly di£Ferent. Now capillary action has a similar effect on
concentration as a large increase of superincumbent pressure ; and
the carbonic acid present in the film of moisture which covers all
articles during the rainy season, or in the film separating two surfaces
in apparent contact, carbonic acid is in a much more concentrated
state than corresponds to the atmospheric pressure. Such carbonic
acid is capable of displacing the silicic acid of natural and artificial
silicates. Here it is where the mischief comes in. Hence tlie crusts
of sodium and potassium carbonates found plentifully in nallahs of
Chota Nagpur and Bchar during the dry seasons ; hence the dimming
of surfaces of glass slides in contact with each other ; hence the film
which ruins lenses kept in confined situations.

**A chemical change of considerable importance to people having
to do electrical testing is the oxidation of the sulphur in ebonite with
the consequent formation of sulphuric acid. This change proceeds
with considerable rapidity especially during the rainy season. Appa-
ratus which are constantly in use and which therefore are frequently
wiped down suffer comparatively little. If, however, the insulation of
ebonite parts should be found to have broken down, it is best to moisten
them with some dilute caustic potash solution, wash them with plenty
of hot distilled water and rub them dry with a clean cloth. Having
mentioned ebonite, I am reminded of india-rubber tubing and rubber
stoppers. It is astonishing how rapidly they deteriorate in this country
The best way of keeping rubber stoppers is to put them into a wide
stoppered glass jar at the bottom of which is placed an inverted per-
forated dish to serve as a support for the stoppers after pouring some
oil of turpentine on the bottom of the jar. Stoppers which have acquired
a hard cracked surface can be softened by proceeding similarly, only
using chloroform instead of turpentine. A good way of preserving
rubber tubing is to give it a coating of gljrcerine. Guttapercha bottles,
such as are used for storing hydrofluoric acid, are best protected by
covering them all over with paper gummed on.

*' I shall not take up your time by dealing in detail with the omni-
present microbe ; with the nitre-producing microbe which covers our
walls and instrument-pillars with destructive inflorescences. Neither
shall I occupy myself with the fever -amoeba which causes more havoc
and financial loss than many a more quickly acting bacterium ; its effect
on instruments and machines is only indirect, although sometimes patent
enough. More direct is the action of mould. I have often observed
beautiful specimens of Mucor growing on ivory parts of apparatus, for
instance on ivory pins and eyelets used for insulation. It is chiefly new
apparatus which are thus affected, just as it is the new binding of books
which suffers most acutely from the attacks of mould. But as only
certain constituents of the ivory or the binding of books supply food-
stuffs to the growing mould, the latter disappears as soon as those
nourishing materials are exhausted. Free circulation of air and plenty

1903.] OF PLANT FOR AND IN BENGAL : DISCUSSION. 104»

of light are probably the most powerful preventatives of mould-
growth."

Having had to refer to dust and dirt, he adds, " I do not think that
people out here are always as careful as they might be in protecting
their machinery from the deteriorating influence of grit and dust. One
sometimes notices even in Europe-bred Europeans a tendency to fall in
with the views and habits of the natives. Of course, as regards dust
it matters little where a carpenter's bench or a blacksmith's forge is
placed ; an open shed with a dust-generating mud floor is about as
good as anything for ordinary work. But it does make a diflFerence
whether first-class machinery, especially dynamo-electric machinery,
but also finer lathes and milling machines, are plumped down on a
gritty mud-floor or in a cobwebby, dark, damp corner, or whether the
machines are placed in a well-lighted machine room provided with a
proper brick-on-edge or patent stone floor. It is true a 'pakka' floor
costs money ; but the ruining of good machinery by grit is not exactly
a cheap operation either. There is another superstition alive in the
minds of some people, and that is that a dark corner is necessarily a
cool corner. This is by no means the case ; 85^ Fahrenheit in a dark
damp room is often less bearable than 95° Fahrenheit in a well-aired,
well-lighted room. It is quite true that the Indian coolie is accustomed
to dirty surroundings, and although hardly thriving on dust and dirt,
the coolie feels quite happy in it. But even he is not accustomed to a
life in dark confined rooms. A great part of the Indian's life is really
spent in the open air and in sunlight, and he will do his work all the
better and the more cheerfully if you give him plenty of air and light
in your workshops. Probably the best position in Bengal for an engine
and machine room is to have its length in a north-south direction. It
should have large venetianed doors in the south and north walls, plain
walls on the east and west sides, and in these walls a row of large round
or square windows higher up near the ceilings. This arrangement
provides a good through-draught and plenty of light."

Mr. C. T. Williams observed that the paraflin wax used in the Mr.
manufacture of instruments at home appears to be softer than that ^Viihams,
imported into India for use in the country. This is specially prepared
to resist high temperatures. For preventing rust this speaker found
that Rangoon oil (the imported, not the local article) was excellent,
and that a satisfactory way of storing bright steel parts of instru-
ments in damp climates was to wrap them in paper soaked in Rangoon
oil. The Indian Telegraph Department had not hitherto manufactured
resistance coils with manganin wire, but this was about to be tried.
He was interested in learning that this metal was, in a slight degree,
liable to rust, but as the wire would be double silk covered and soaked
in paraffin, there would be no reason to apprehend that it would be in
any way injured. This speaker drew attention to the very bad work
put inside induction coils by some makers at home. It was no un-
common thing to find a coil fail owing to soldered joints being corroded
through, this being due to the fact that resin had not been used for a
flux. The connection to the condenser was also very faulty. This

1044 BRUHL : ON THE PRESERVATION AND PACKING [Calcutta,

Mr sometimes consisted of a piece of wire pressing on the tinfoil, and kept

in place by a piece of board. The board warped and the connection
failed.
Mr. Eustace. Mr. S. EusTACE Said that the conditions prevailing in a hot moist
climate were such that it appeared almost impossible to make the mind
of an European manufacturer, dwelling in cooler climes, understand.
He well remembered at one time writing to a manufacturer and giving
him some ideas that would be useful to him in designing machinery for
use in India. Instead of gratefully tendering his thanks, he quietly said
that as he had been designing machines from the time he (the speaker)
was still in petticoats, or a suggestion to that effect, the speaker could
not teach him anything. He did not suppose that it was always possible
so to design a sensitive instrument, and despatch it, however carefully
packed in its working state, that it could be sent by rail in the United
States. Manufacturers, however, seemed to think differently, and
instead of taking a delicate instrument as much as possible to pieces,
and packing the pieces separately, they seemed to consider it sufficient
to stuflF the moving parts up with silver paper and pack the instruments
in straw ; and in the latter propensity some seemed to be incorrigible.
He admitted, however, that in one direction it was very difficult to pre-
serve instruments properly on the voyage out. The consumers* meters
sent out for the Calcutta Electric Supply Corporation, although excel<-
lently packed in hermetically sealed cases, as often as not arrived with
pinions and gear wheels covered with rust. He would suggest that in
a case like this, where the rust must be due to sweating inside the case,
that all the cases should be well dried with unslaked lime before receiv-
ing their contents, and being sealed up. In the other direction, how-
ever, that of mechanical injury due to bad packing, lay one of the chief
causes of complaint. The probabilities were that the actual man who
did the packing had just about the same amount of conscience as a
coolie.

He did not remember any case of a dynamo being burnt out from
heat, pure and simple, without some other cause at the back of it. The
springs on some of the meters recently imported had been gilded, and
this he found fairly satisfactory, though he had had much trouble with
ordinary springs previously. He had had cases where a resistance of
manganin steel, after withstanding heat for a certain length of time,
had disintegrated so that it crumbled in the hand.

There was no question as to what was the fundamental difficulty in
preserving instruments and machinery in Calcutta — it was the climate,
which had often the same effect on men. Temperature was often a
great trouble, and during the hot weather he had known the tempera-
ture on the station switchboard to be as high as 112^ Fahrenheit, and
this with an atmospheric humidity of over 90.

As far as dynamo machinery was concerned, it was advisable to
have all the windings well baked before being put into use. He had
done this lately with the fan armatures, and the result had been very
beneficial.
sini son ^^' ^* ^* ^IMPSON would likc to add a word as regards telegraph

and telephone instruments. In these instruments it was impracticable

1903.1 OF PLANT FOR AND IN BENGAL: DISCUSSION.

1045

to avoid the use of wood, but all woodwork must be dovetailed or Mr.
screwed together, and no reliance whatever could be placed on glue.
Also the instrument must be so designed that its proper working was
quite independent of any warping or shrinking of the wood which
might occur. He stated that they had in the Telegraph Department
used german-silver wire for their resistances, and found it last very
well. They were, however, now experimenting with some of the other
materials on the market.

Mr. H. H. Reynolds remarked that the condition of cases on receipt
depended very largely on the time of the year when they came through
the Red Sea. The manufacturers insisted on using straw to a large
extent, and in hot weather it invariably rotted and caused damage.
He had had a case where a few straws fell and adhered to a greased
shaft, and when opened in Calcutta the rust had eaten into the steel.
He quoted a case of a large engine packed in England for transit to
Calcutta, which was fixed into the packing case by wedges driven in
between the cylinder lagging and the case, with the result that con-
siderable damage was done. The speaker believed American packing
to be the best, and suggested that this might be due to the extremely
rough handling which cases received in America, as pointed out in the
paper. He stated that nearly all the ordinary types of instruments
rapidly deteriorated when kept in Calcutta ; so that after a short time it
was not unusual to find inaccuracy amounting to 5, 10, or even 20 per
cent. In one case a potentiometer was sent out to him packed in such
a way that when opened up it fell to pieces, and yet when it was
returned to the manufacturers packed in exactly the same way they
complained !

Mr. J. C. Shields was glad to see attention drawn in Professor Briihl's Mr. Shields.
paper to the indifferent way in which instruments sent out from home
were sometimes packed. The matter was of great importance in India,
and he hoped manufacturers at home would take note of the author's
remarks. He remembered on one occasion some delicate instruments
being sent out by a firm in Paris. They had been most carefully en-
closed in a tin-lined case ; but the packing consisted of straw which
had not been dried. The instruments were in consequence subjected
on the way out to a vapour bath for several weeks, and all the iron
parts were a mass of rust.

Mr. J. Williamson remarked that the best way of keeping cases the
right side up during transit was to fix battens underneath them, which
would lend themselves to the shifting of the case on rollers and which
would show better than any label how the case was intended to be
placed. In the case o instruments he suggested that it might be
possible to avoid damage due to moisture during transit by enclosing
at small quantity of calcium chloride in a special cover inside the box,
as was done by manufacturers of sensitive photographic papers.

Mr. A. H. PooK said that the Home Institution appointed com- Mr.Pook.
mittees for the purpose of considering all sorts of matter of interest to
manufacturers, and he was sure that if they would appoint one on the
science of packing for export they would be not only doing the home
people a good turn, but would assist users and consumers living abroad

Mr.

Williamson.

1046 BRUHL : ON THE PRESERVATION AND PACKING [Calcutta.

Mr. Pook.

Mr. Meares.

Mr.

Mclntyrc.

Father
Lafont.

a great deal in a way which ought in some way to recompense them
for our late increase in annual subscription and curtailment of our
free literature.

Mr. J. W. Meares said that judging by previous speakers and by the
experiences one constantly heard of, the packing question was at the
root of the whole matter, and he thought we should take steps to place
this most interesting paper and discussion before the home manufac-
turers, so as to advise them of their shortcomings. Where coolie transit
of goods was necessary in the hills, foreign manufacturers would under-
take to keep the weight and size of nearly all packages within reason-
able limits for the purpose, but the British manufacturer knew better
and made not the least effort in this direction, with the result that much
damage was sustained. It might be noted that natives of this country
had not the remotest notion of shifting heavy packing cases by means
of rollers and bars, or of opening the lids by recognised methods. If
these points were fully considered something would have been gained
in the way of making the packing suitable for the treatment it was
likely to receive. Again, it was no uncommon thing for a steel shaft
to be packed without any protective grease or paint, and as likely as
not the case in which it was enclosed would be extremely damp, so
that the fact of soldering it up was not of the least good. As an
endeavour to meet the trouble which every one experienced in the
rainy season, he had constructed a large drying box in which to keep
some of his special instruments during that season, and in a tray at the
bottom he was putting calcium chloride to dry the air. The case was
made to close on thick felt, so that he hoped it would also entirely
prevent the ravages of rats and insects.

Mr. A. N. McIntyre said that he did not know whether any of the
members of the Calcutta section had experienced the trouble he had
had with the reddish enamel finish given to portable Weston instru-
ments; it became spotted and dull-coloured in patches on exposure.
The case was of brass and there was no reason why it should not
be lacquered, which though not rendering it proof against climatic
influences would at least be preferable to the enamel.

The portable Kelvin- voltmeters supplied us were to all appearances
either encased in aluminium or aluminised iron ; if it was the latter he
could not say much for the process as a corrosion-resisting agent,
whatever it might do for iron in contact with salt water. The author
of an article in one of the Electrical papers recently referred to an
almost perfect solder for aluminium, but unfortunately did not give its
composition. While speaking of solders he would ask if the author
saw any objection to the use of soft bismuth solder fusing at 320° F. for
repairing galvanometer suspensions, since it greatly simplified the task.
He had tried it on one of his galvanometers with very fair results,
though of course it would not do for resistance coils.

The Very Rev. Father E. Lafont (Chairman), in closing the dis-
cussion, said that most of the remarks which he intended to make on
this very interesting paper had been forestalled by other speakers.
He had thirty-five years' experience in the care and use of instruments
in India, and he suggested that it would be highly desirable that the

1903.] OF PLANT FOR AND IN BENGAL : DISCUSSION. 1047

Local Section should move the I. E. E. to take up the question of Father
inducing manufacturers to attend to the special needs of India. .aont.

The legs of statical instruments should on no account be fixed on
with shellac, and in this point the manfacturers failed to appreciate the
diflFerencc of climate between Europe and India.

As regards packing, Father Lafontp considered that it would be
better always to get instruments out in parts and to set them up in
India, since the users of electric instruments would generally be com-
petent to do this, or should be so ; the makers would then perhaps
learn to pack the separate parts so as to be immovable, and he would
suggest that they should give their packers a course of lectures on the
subject of inertia, which they seemed generally to ignore.

As regards rubber tubes and stoppers he enquired if there were any
satisfactory method of keeping them. [Professor Briihl here suggested
glycerine as a preservative.] He stated that for ebonite, darkness was
essential. With reference to a previous speaker's remark he suggested
that the decomposition of unpolished ebonite would be greater than
that of the polished article, as the rough surface, being less dense and
hard, would probably be more easily disintegrated by exposure.

Professor BrOhl in reply, after referring to the remarks of several Prof. Bruhi.
speakers, said the chief advantage of using ebonite in an unpolished
state, especially in the case of corrugated supporting pillars, was that
one could always get a fresh and highly insulating surface by giving it
a few touches with fine glass paper.

Some German makers had adopted, for the purposes of articles
specially manufactured for tropical countries, what they called a
tropical outfit, which he could highly recommend ; all metal parts
were strongly nickelled, and any Nicol's prisms, which, for instance,
might form adjuncts of photometric apparatus, had their calcspar
rhombs protected by cover-glasses cemented on with Canada balsam.

It was quite possible that light had something to do with the rapid
deterioration of certain kinds of material ; but he was under the
impression that the influence of light was often exaggerated, especially
where, as in Bengal, the sky was commonly covered with a haze, which
was almost certain to absorb a considerable percentage of active rays.
Several instances of destruction which he had heard described as due
to the action of light could almost with certainty be traced to the action
of dampness and fungoid growths.

For years he had used a device to keep dry one of his balances as
well as a Clifton electrometer. He had replaced the top of the balance
case by a shallow box having a perforated bottom, and placed shallow
trays containing pieces of fused calcium chloride in the box. The
electrometer he had housed in an outer case with a similar top to it.
Materials for drying the air should be placed on top ; materials for
absorbing carbonic acid should be kept at the bottom. As concen-
trated sulphuric acid began to dissociate at about 30° C. with the
formation of volatile sulphuric anhydride, sulphuric acid should not be
used in India as a desiccating agent, just as it could not be used for
the greater part of the year as an absorbent of water vapour in
chemical analysis.

1048 BRUHL : ON THE PRESERVATION AND PACKING [Calcutta.

Prof. Bruhi. ^g regarded dynamos, the chief trouble one had was about insula-
tion. He should advise his friends to specify that armatures and field
magnet coils should have every layer of conductors well painted with
good shellac varnish or some equally effective composition, and after
finishing to have them well baked. If this were done, and if in India
the dynamo were properly hoftsed, he did not think there should be
much trouble about the insulation breaking down. But there was no
good complaining about heat and dampness and nitre, and so on. They
had plenty of them and to spare ; but as practical politicians they must
take means to circumvent those injurious agents. If they placed a motor
in a pit which was liable to be flooded, they must not blame Providence
if the pit did get flooded and the armature burnt out in consequence.
If they placed a dynamo in a shed, a couple of inches above a mud-floor
and with no possibility of air-circulation, they must not be astonished
if the dynamo got ruined by dust, dirt, dampness, and other damaging
influences. Damp surroundings produced consumption even in electric
machinery.

He did not believe that the life of a good accumulator cell, provided
the cell were carefully treated, was much shorter in India than in
Europe. But he too had had a fearful experience with a battery. The
type of cell was not the kind he had specified, although it was a cell
the praises of which had been sung by more than one English authority
and in more than one text-book. Luckily the company who manu-
factured that battery went into liquidation soon after and could do no
further harm. But his battery was really a sight worth seeing, after it
had been working for six weeks ; every positive plate had buckled into
the shape of a cocked hat ; and one might straighten them, but in a few
days there was the cocked hat again. Of course, he had always been
very careful about maximum charges and discharges ; his battery had
been in work practically without interruption, and he had never allowed
it to stand without its being charged up at frequent intervals.

He would like to point out to those who had to order instruments
the advisability of completely specifying their requirements. After all
they must not expect home firms to find out themselves everything
about the tropics. When ordering thermometers, he always specified
that the capillary tube must end in a small reservoir of a sufficient
capacity to receive the overflow mercury up to a temperature of 45^ C.
He had nearly always found the firms from whom he had obtained
instruments ready to receive suggestions and to act on them. Now
and then one did come to deal with a firm who' thought that they had
nothing to learn ; but as soon as he found that out, that firm obtained
no further orders from him. On the other hand he knew of firms who
had made special experiments on wood suitable for tropical climates.
There was one firm who had taken a great deal of trouble in trying to
evolve a safe system of packing dynamos for shipment to distant
countries. Among the worst offenders were the packers of such things
as switches, fuses, etc., anything especially that had porcelain parts.
It was very easy to pack these articles so that they could be damaged
during transit. The principle which should be acted on in packing
fragile articles was to fix them rigidly to some rigid support, but to have

1903.] OF PLANT FOR AND IN BENGAL : DISCUSSION. 1049

the supporting frame suspended from or supported by springs, the P«>f. Briihi.
frame being protected from excessive vibrations by layers of fine
shavings. He had spoken about the probable influence of the sea
voyage. In most cases, however, the mischief was clearly traceable
to damp straw or shavings. Straw should be prohibited as a packing
material. If possible, one should order one's goods to be sent off from
Europe between May and September, or at any rate at a time when
there was no slush or soft snow on the ground. He found that the
packing cases were filled with what looked like stable litter whenever
the case had been despatched during the winter months. In any case
he joined with his confreres in the expression of the hope that the Parent
Society might be moved into seriously taking up the subject of packing
for shipment to distant countries.

1050 TAITE AND DOWNE : AUXILIARY PLANT [Manchester,

MANCHESTER LOCAL SECTION.

COMPARISON BETWEEN STEAM- AND ELEC-
TRICALLY-DRIVEN AUXILIARY PLANT IN
CENTRAL STATIONS.

By C. D. Taite, Member, and R. S. Downe, Associate

Member.

{Paper read at Meeting of Section on April Jth^ 1903.)

Although the competition for economy in the working of Electrical
Generating Stations has now become exceedingly keen, yet the widely
different figures obtained annually as the result of the year's working
of the many generating stations now in existence lead one to believe
that other factors besides the price of fuel and the personnel of the
staff affect the figures to a very appreciable extent. The authors are
of opinion that the choice of auxiliary plant, for instance, may exercise
a strong influence for economy or otherwise, according as the selection
has been made, wisely or the reverse ; they have therefore endeavoured
in this brief paper to put forward some results obtained from plant
under normal everyday conditions, in the hope that the figures given,
being such as can be obtained from similar plant in any generating
station and not the result of full-load tests only, may prove of some
practical utility to those who from time to time are called upon to
purchase central station auxiliary plant.

That the subject embraces a wide variety of machinery may be
seen at once from the following list of auxiliary plant to be found in
the majority of stations of fair size, and which are driven by steam
engines or electric motors : —

Air Pumps for Condensers.
Cranes.
Feed Pumps.
Mechanical Stokers.

Economisers.
Coal Elevator.
Ash Conveyor.
Workshop.

During recent years it has become the practice to use electric
motors almost exclusively for driving the greater number of the above
adjuncts of the generating station ; for instance, cranes, stokers, econo-
misers, coal elevators, ash conveyors, and workshop are generally now
found driven electrically ; but condenser air-pumps and also feed-water
pumps still adhere to a large extent to steam power ; the latter two
auxiliaries are running continuously, the running of the others being
of an intermittent character. It is, however, becoming increasingly
recognised that, quite apart from the power required for driving the
plant, the loss from condensation in long ranges of steam piping which
are rendered necessary when steam auxiliary plant is used is quite
appreciable, and compares badly with the small amount of power

1903.J IN CENTRAL STATIONS. 1051

absorbed in the cables of an electrical installation. Another important
advantage which electrical methods of driving have over steam power
is the ease with which the power taken in the former can be measured,
while in the case of steam it is next to impossible to state definitely
what is the percentage of power absorbed by the auxiliary plant. In
the new generating station of the Salford Corporation, where the whole
of the auxiliary plant is driven electrically, it is found that the percentage
of power absorbed by the auxiliary plant varies from 8*3 per cent, to
6*5 per cent, of the total power generated, according to the state of the
load factor ; it is clear that the better the load factor the lower will this
percentage be reduced. The following figures are those of an average
week taken from the station records : —

Table I.
Units Generated 148,851

Units used on Works

Made up as follows : —

Condensing Plant

Boiler Feed Pumps

Mechanical Stokers

Ash Conveyor

Economiser Scrapers (1,600 Pipes)...

Coal Elevators ,

Workshop

Engine-room Crane

The power taken by the mechanical stokers represented 1*04 units

per boiler-hour, which is a rather higher figure than that obtained in

many previous weeks, while the economisers required 0*33 unit per

hour for driving the scrapers for each battery of 400 pipes ; the coal

elevators absorbed 0*22 unit per ton of coal raised 40 feet and

deposited in the bunkers. The load factor for the week was

. / Units generated x 100 \ ,, ..

301 per cent I vi i — j ..\^ .u — rJ' as all the power

•'^ ^ VMax. load x No. ot hours m week/ ^

circuits in the works arc metred, it will be seen at once how easily
one can check the whole of the power taken by the auxiliary plant
when that plant is driven electrically ; if in any week abnormal figures
are obtained, it is a very simple matter to find the cause, as the weekly
or even daily returns show clearly on which plant the abnormal con-
sumption is taking place. This fact in itself tends to promote economy,
as one soon finds out whether the plant is giving the duty that may
fairly be expected from it ; a standard of efficiency can thus be set up
beyond which the plant must not be allowed to fall.

To turn now from a general comparison to an individual case, it
will be generally admitted that there is no more important auxiliary
plant in a generating station than the feed pumps ; for, unless the
pumps are reliable and trustworthy, the supply of steam for the main
engine cannot be guaranteed. It is therefore a matter of the utmost
importance to make a porrect choice of the type of feed pump.

Pcrcentane of Units

Generated.

9,687 ..

650

6,962

4-67

1,758 ••

ri8

555

037

0-07

157

o-ii

76 ..

005

65 ..

005

—

1052 TAITE AND DOWNE : AUXILIARY PLANT [Manchester,

The points which have to be considered are —

1. Reliability.

2. Economy in working.

3. First cost.

4. Upkeep.

Reliability.

Provided that the plant is ordered from experienced firms, there
need be no doubt about the reliability of feed pumps, whether they be
driven electrically or by steam ; both types are equally satisfactory on
this score. Those who have any doubt as to the absolute reliability of
electric motors have only to consider the case of the tramcar motor,
which is working under the most difficult and trying conditions, yet a
breakdown of a tramway motor is quite a rare occurrence. How much
more reliable, therefore, should a pump motor be which is working
under conditions so much more favourable. Nothing more requires
to be said to show that, whether the pumps be driven by steam or by
electricity, there need be no question as to any want of reliability.

Economy ix Working.

Until the advent of the electric motor, steam pump makers appear
to have devoted all their attention to making their pumps reliable, and
to have left the question of efficiency to look after itself ; lately, how-
ever, owing to the competition of the motor and to the much improved
figures obtained by electric driving, they have been compelled to
seriously consider their position, with the result that steam feed pumps
can now be obtained which give results immensely superior to those
of a few years ago. Still, owing to the nature of the work which they
have to perform, steam feed pumps can never compare in efficiency
with the main engines installed in the generating station for generating
electricity. One well-known firm of pump makers state the steam
consumption of their standard 6,000-gallon pump to be as follows : —

Gallons
delivered.

1,000

2,000

4,000

6,000

Tests have been carried out at Southport on pumps which have
been in use for three or four years, and the following was the average
result of several tests each extending over twenty-four hours under
ordinary working conditions : —

Lbs. of water delivered per lb. of steam used ... 49*1
The pumps had been recently thoroughly overhauled and fitted with
new pump rings ; the great discrepancy, therefore, between the figures
obtained and those given by the pump makers must be due to the
intermittent character of the load, which wa§ 2({ the averjige rate of
1,460 gallons of water pumped per hour.

Table IL

Lbs. of Steam used per Hour

Lbs. of Water deli\ ;red

at 160 lbs. pressure.

per

lb. of Steam uscd.

130

...

253

...

490

...

8i-5

714

...

Table

III.

Duration of Test

4 hours
4 i»

1903.] IN CENTRAL STATIONS. 1063

At the Salford station tests have been carried out on an electrically-
driven 4,000-gallon pump with the following results : —

Gallons delivered. Duration of Test. Units used.

(i) 8,971 4 hours 27'6

(2) 15,822 4 „ 36

If each unit is taken as requiring 30 lbs. of steam to generate it,
which is more than 25 per cent, above the full- load consumption of the
steam engines installed, the above figures may be stated as follows : —

Table IV.

Gallons delivered Lbs. of Water delivered

per Hour. per lb. of Steam used.

2,240 108

3,955 147

Comparing these figures with the figures given above, it will be
seen at once how greatly superior the electrically-driven pumps are
from the point of duty per lb. of steam than are the steam pumps, and
this too in spite of the fact that the full-load overall efficiency of the
electrically driven pumps was only 60*67 P^r cent. The motor in this
case was coupled to the pump through worm gearing, which at the time
of the test was, comparatively speaking, new, and which is certainly
giving better results now. The ratio of the gearing is 12 to i. It
would be interesting if some one could give particulars of tests of
pumps electrically driven through spur gearing or by other means.

With regard to the figures obtained at the Southport works, it will
be seen that they compare very badly with the electrically-driven plant,
and on the basis that the latter absorbs i'i8 per cent, of the total output
of the station, the former must be requiring from 2 J per cent to 3 J per
cent, of the total output. This is a serious matter, particularly where
the price of coal is high, for it is unnecessary to point out that the
higher the price paid for fuel the more important does it become to
instal economical plant.

The figures given by the pump makers are interesting as showing
how slight is the increase in efficiency of a steam pump from light load
to full load. The electrically-driven pump, on the other hand, dehvers
36 per cent, more water per lb. of steam at full load than it does at half
load. This points to the desirability of a careful sub-division of plant
where electric motors are adopted.

First Cost.

With regard to the money value of the saving in power, this varies
directly with the price of fuel, and inversely as the first cost of the
plant. In Lancashire, where good slack can usually be obtained for
8s. 6d. to 9s., the money value of the steam saved is less than half what
it would be in London and south-country towns, where fuel ranges from
20s. to 30s. a ton.

Vol. 8?. 70

1064 TAITE AND DOWNE : AUXILIARY PLANT [Manchester,

Still, taking again the Salford figures, i per cent, of the present
annual coal bill represents £60, and to put the saving in fuel at this
station due to the use of electrically-driven pumps instead of steam
pumps at ;£ioo per annum is a conservative estimate. Against this
saving has to be set the additional interest and sinking fund due to
the extra cost of the electrical pumps ; say for a 5,000-gallon pump
;£330i against ;£i25 for a steam pump ; allowing 6i per cent, in each
case and the provision of three pumps, the difference per annum would
be £40, which reduces the money value of the saving to £60. This
may seem a small sum, but it should be remembered that it represents
the minimum saving.

Upkeep.

With regard to the question of upkeep there is little if an)rthing to
choose between the motor-driven pump and the steam pumps provided
that both are well looked after and kept in a proper condition. Care,
however, must be taken to see that the delivery range attached to the
pumps is provided with a relief valve of ample area to prevent any
damage occurring even should the fireman close all his feed valves.;
otherwise the effect would be to cause a fracture either of the pipes or
the pump casing.

The case, therefore, with regard to feed-pumps may be summed up
as follows : —

1. Reliability. — Both types equally reliable.

2. Economy in working. — The electrically-driveli pump shows a

great superiority.

3. First cost, — The electrically-driven pump costs about three

times as much as the steam pump.

4. Upkeep. — Both types satisfactory.

Generally speaking the authors are in favour of electricallj'-driven
feed pumps, particularly in localities where coal is dear. Where such
pumps are used, and in fact where any electrically-driven auxiliary
plant is extensively adopted, the authors consider that a battery of
accumulators is a practical necessity, as in the event of a total break-
down of the generating plant from any cause, the supply of water to
the boilers and the lighting of the works would not be interrupted.

Turning now to the consideration of condensing plant, it will be
seen from Table L that the condensing plant at the Salford works
absorbs no less than 4*67 per cent, of the total output of the station.

The plant consists of eight sets of jet condensers each provided
with an Edwards three-throw air-pump driven electrically through
double reduction spur gearing. Each condenser deals with the steam
exhausted from a 1,200 H.P. engine, and the water for condensing this
steam is drawn from the Manchester, Bolton and Bury Canal. One of
the conditions being that the temperature of the discharge water shall
not exceed 90° Fahr. it is frequently necessary to use a rather excessive
amount of circulating water. The percentage of power taken by the
condensing plant when the engine is working fully loaded is 2*4 per
cent. This compares with i^ to 2 per cent, which is the usual allow-
ance when the air-pumps of a jet condenser are driven direct from the

1903.] IN CENTRAL STATIONS. 105d

main engine as in mill work ; the latter practice is undoubtedly the
most economical, as the losses in the dynamo and motor are both
saved ; but with the modern high-speed engine a direct-coupled con-
denser is, generally speaking, impracticable, and the choice lies between
a separate steam engine and an electric motor. The latter is generally
the most convenient to adopt on account of cleanliness and small space
required, but the advantage with regard to economy in power rests, if
anything, with the steam plant run condensing. Where surface con-
densers are used the conditions favour the use of electric motors, and
the authors recommend their more frequent adoption.

At Southport interesting figures have been obtained in connection
with the use of single-phase alternating-current motors driving Gwynne
centrifugal pumps for raising water for Korting's ejector condenser.
The total lift is 35 feet, the volume of water lifted is 60,000 to 66,000
gallons per hour per engine, and the horse-power of the motors is
35 B.H.P. ; the engines to which the condensers are attached are of
1,000 H.P. ; during a three hours run the alternator generated an
average of 510 units per hour, full load being 600 k.w., and the motor
pump took 29*6 units per hour, 5*8 per cent. ; the percentage power,
however, during the evening's run, averaged as much as 7*26 per cent,
of the units generated. As the condensing plant requires a constant
supply of water irrespective of the load on the engine, it is evident that
when the alternator is generating its full load (600 k.w.), the percent-
age of power taken by the condenser would be reduced to 4*93 per
cent., still a high figure.

A last example of an electrically-driven plant is a motor alternator
set at the Salford Corporation Works, used for supplying the outlying
districts with alternating current. There are two sets in duplicate, each
consisting of a 150 k.w. direct-current motor, direct-coupled to two
120 k.w. alternators; the latter is of an old-fashioned design, having
been built in 1894. The two sets are never run together except for the
purpose of changing from one to another ; one set just takes the full
load every night, but during the daytime the load is very light. The
average daily efficiency taken over several weeks in the winter amounted
to only 72 per cent., the load factor of the plant being 35 per cent. ; the
maximum full-load efficiency is 84 per cent. This example is given
to show the care which must be taken in designing a direct-current
supply from an alternating-current generating station when a reasonable
efficiency is to be obtained.

A few figures relating to eleven months' working of the auxiliary
plant at Salford may be interesting. The total units used during this
period by the auxiliaries amount to approximately 410,000, equivalent
to 7*o per cent, of the total units generated ; as the cost of fuel is just
o*25d. per unit generated, the money value of the units is £^2'j. There
is no doubt that the auxiliary plant is partly responsible for the low
coal cost per unit generated, as it has helped to improve the load factor
very materially of the generating plant.

Managers of electricity undertakings spend a large proportion of
their time in advocating the adoption of electric motors in the interests
of the consumer, and with a view of improving the station load factor ;

1056 TAITE AND DOWNE : AUXILIARY PLANT. [Manchester,

consequently, it is essential that wherever possible they should arrange
for electrical driving on their own works.

In conclusion the authors feel that they must apologise for so
frequently quoting the figures of the stations with which they are
connected ; they have been compelled to do so owing to the paucity
of other information at their disposal ; they trust, however, that their
remarks may serve the purpose of eliciting information from other
central station engineers with a view of ventilating a subject with
regard to which reliable data is not at present easily available.

1903.] GIBBINGS: THE CARRIAGE OF GOODS. 1067

MANCHESTER LOCAL SECTION.

THE CARRIAGE OF GOODS ON ELECTRIC v/
TRAMWAYS.

By Alfred H. Gibbings, Member.

[Paper read at Meeting of Section, April 21s/, 1903.)

The many questions involved in the carriage of goods have always
been of supreme importance to manufacturing communities in ail
countries. At the present day when keen international competition
is so strong, every improvement in the direction of economy of both
time and cost gives an immediate advantage where it is adopted. I
need only refer to such a scheme as the Manchester Ship Canal in the
illustration of the enormous importance attaching to this subject. But
we are not concerned in this paper with the various methods and
details of long-distance transit. For long distances both railway and
canal carriage are at present essential, and it is true of each that an
increased through traffic and lessened local traffic would tend to
cheapen existing rates. On the other hand, neither railway nor canal
will ever be capable of such extension as to avoid the necessity for the
subsidiary use of carts or other vehicles for the collection and
distribution of goods, and it is these charges which so largely increase
the cost of transportation.

The charges and rates which are at present levied for long-distance
transmission may be likened to the reduced charge for electric energy
possible only to the long-hour consumer on an electric lighting system.

In these cases the " standing charges ** rate is reduced in proportion
to the length of route or time respectively. A similar analogy exists
between the short-distance charges for conveyance of goods by railway,
road, or canal, and the short-hour electric light user. Each has to bear
a large proportion of the " standing charges " rate. These *' standing
charges " in the case of goods conveyance consist of heavy interest on
rolling stock due to the very low earning capacity on short runs,
increased proportion of handling and transhipment costs, station
terminal charges, warehousing, etc.

Some of these charges are, of course, bound to occur with any
system of handling and transporting goods, and the nature of the
goods has also to be taken into consideration, but I propose to show
in this paper some of the possibilities of cheapening the cost of
conveyance by utilising electric tramway and light railway systems.
By the term " short-distance traffic " I refer to conveyance up to fifty
miles, but particularly to distances varying from five miles to thirty
miles.

1058 GIBBINGS: THE CARRIAGE OF GOODS [Manchester,

Areas of Connected Tramway Systems,

In order to inaugurate and carry on successfully such a scheme, it is
necessary to have a considerable area covered by tramways with tracks
of uniform gauge. Such an area is illustrated in Fig. i.

This area includes the following lines, viz. :—

Liverpool Corporation

Liverpool and Prescot Light Rail-
way

St. Helens Tramways (Leased by
the Corporation to a Company).

South Lancashire Tramways

Wigan Corporation

Bolton Corporation

Bolton, Turton and Darwen Light
Railways

Darwen Corporation

Blackburn Corporation

Accrington Corporation

Farn worth Urban District

Radcliffe Urban District

Whitefield Urban District

Bury Tramways Company

Rochdale Tramways Company ...

Warrington Corporation

Salford Corporation

Eccles Corporation

Manchester Corporation

Oldham, Ash ton and Hyde Tram-
way Co „ 4 ft. 8^^ in.

Stalybridge, Hyde, Mossley and
Dukinfield Tramways and
Electricity Board „ 4 ft. 8i in.

Notwithstanding the very complete system described above, it will
nevertheless be apparent from the map that much yet remains to be
done to reach many of the mill districts, collieries, and outlying town-
ships in order to obviate as far as possible the cost of transhipment,
handling, and cartage.

Some considerable attention has already been given to the carriage
of goods on electric tramways, the first proposal emanating through
the Liverpool Chamber of Commerce in a scheme submitted by Mr,
J. T. Wood on October 14, 1896. Mr. Wood says : —

" It is necessary that I should now point out to the Committee that
no new departure or principle is involved in the proposal to use
tramways for the carriage of goods, nor would it be necessary, in
obtaining powers for the proposed tramways, to get any special
permission to use them in that mannei\ . . . The goods and materials
for which charges may be made arc specified in a minute way, and
include, for instance, coal, lime, iron, bricks, castings, sugar, grain,

Gaug

e 4 ft. Si in.

4 ft. 8i in.

3 ft. 6 in.

4 ft. 8i in.

4 ft. 8J in.

4 ft.

4 ft. 8i in.

4 ft. 8J in.

4 ft. 8i in.

3 ft. 6 in.

4 ft. Si in.

4 ft. 8i in.

4 ft. 8i ip.

4 ft. 8i in.

1903.] ON ELECTRIC TRAMWAYS. 1069

corn, flour, cotton, wools, fish, etc. A charge is also prescribed for
iron boilers, cylinders, and articles of great weight No objection
could, therefore, be raised to the scheme on the ground that it was
intended to use the tramway in a way which has not been contemplated
by the Legislature ; in fact, the general tendency of legislation during
the past few years has been in the direction of furthering the trade of
the country by the construction of light railway systems."

In referring to this scheme of Mr. Wood's, I must include among
the preliminary movements made in the United Kingdom to put into
practical effect light railways for goods traffic, that of the inquiry of
the Liverpool Chamber of Commerce, whose report, issued on July 22,
1898, embodies no less than twelve proposals for the transportation of
goods between Liverpool and Manchester and adjacent centres. The
report contains the discussion on each scheme, and a summary of the
advantages and disadvantages of each.

In April, 1901, I prepared a detailed report on the subject so far as
it applied to the area of the South Lancashire Tramways, and also a
special contribution to Traction and Transmission in April and May,
1901. During the last two years the following literature has also
appeared on the subject : —

"The Conveyance of Goods on Electric Trolley Lines," by A H.
Gibbings ; paper read before the Liverpool Engineering Society on
January 29, 1902.

" Parcels on Tramways," Manchester Evening Chronicle, December 16,
1902.

" Goods Traffic on the Tramways, ' Manchester Guardian, February
12, 1903.

*' Electric Trams and Goods Traffic," Manchester Guardian, November
22, 1902.

" Through Traffic on Tramways for Passengers and Goods," paper
read before the Liverpool Chamber of Commerce July 21, 1902, by
J. E. Waller.

" Running Powers," by A. H. Gibbings ; paper contributed to
Traction and Transmission, April, 1902.

** Some Notes on the Commercial Management of Electrical Tram-
ways," by T. W. Sheffield, Ftelden's Magazine, January and February,
1903.

"The Commercial Management of Electrical Tramways," by C. H.
Wordingham, The Electrical Review, January 30, 1903.

"The Conveyance of Goods on Electric Trolley Lines," by A. H.
Gibbings, paper read before the British Association, Glasgow, 1901.

The following publications also refer to various methods of dealing
with goods traffic : —

" Report of a Special Committee on Light Railways," Incorporated
Chamber of Commerce of Liverpool, July 22, 1898.

" Plateways," by Alfred Holt, Liverpool Printing and Stationery
Company, Ltd., 42, Castle Street, Liverpool, 1899.

" Heavy Motor Traffic in France," by M. Georges Forcstier, The
Journal of Commerce Printing Works, 9, Victoria Street, Liverpool,
1900.

1060 GIBBINGS : THE CARRIAGE OF GOODS [Manchester

" Light Railways/' by J. Walwyn White, F.I. Inst. Widnes, 1895 ;
paper read before the Liverpool Chamber of Commerce and the
Society of Chemical Industry.

" A New System of Heavy Goods Transport on Common Roads," by
Bramah Joseph Diplock ; Longmans, Green & Co., 39, Paternoster
Row, London, 1902.

"Supplementary Report of the Special Committee on Light
Railways," Incorporated Chamber of Commerce of Liverpool, Lee
and Nightingale, 15, North John Street, Liverpool, 1900.

" Light Railways and Agriculture," Electrical Investments Review,
Wednesday, February 4, 1903.

In the foregoing publications many aspects of the question have been
put forward and discussed, and to a certain extent, therefore, the rough
ground has been broken. Reference to these papers should be made
for many interesting features and expressions of individual opinion
which it is impossible to embody herein. For instance, in the writer's
paper read before the Liverpool Engineering Society in January, 1902,
the discussion included remarks by Mr. Brierley H. Collins, M.Inst.E.E.,
Mr. Alfred Holt, M.LC.E., Mr. J. E. Lloyd Barnes, Wh. Sc.,
M.I.Mech.E., and Mr. John A. Brodie, Wh. Sc, M.I.C.E., M.I.Mech.E.
(the City Engineer of Liverpool), and others.

Existing Methods and Cost of Conveying Goods.

The usual methods of goods conveyance at the present time are by
railways, canals, automobiles, and horse-drawn vehicles. Railway
companies have for too long had the sole control of goods traffic.
The full use of existing canals, and the possible construction of others,
would be a step in the direction of economy.

Some attempt has recently been made under the Locomotion on
Highways Act, 1896, to reduce the cost of conveyance of goods between
railway and canal depots and the mills, warehouses, etc., by automobiles,
and an excellent paper on that subject was read before the Liverpool
Self- Propelled Traffic Association on December 3, 1900, by M. Georges
Forestier, who is engineer-in-chicf to the Department of Roads and
Bridges in France.

The principal method, however, of such local conveyance is by horse-
drawn lurries. At the Stalybridge railway goods depot, for instance,
no less than 26 lurries are required to deliver cotton, coal, and other
goods to the various mills within the district. At Hyde 42 are
required, at Mossley 14, and at Dukinfield 10, and in each of these
cases the lurries arc owned by the railway companies.

Table I. gives a list of imports and exports into and from Liverpool
respectively for the years 1898 and 1899. These figures represent the
quantities of goods actually conveyed through Liverpool, exclusive of
those which find their way by the Ship Canal direct to the Port of
Manchester, the statistics of which are, of course, separately kept by
the Custom House authorities as for any other port. I have, however,
considered that the Liverpool statistics are in themselves amply suffi-
cient to illustrate the enormous goods traffic in the area described

1903.]

ON ELECTRIC TRAMWAYS.

1061

TABLE L— TRADE OF LIVERPOOL.

IMPORTS.

EXPORTS,

Year.

Goods. 1898. 1899.
ARTICLES OF FOOD AND DRINK.

Bacon cwt. 2.999.624 2,836.703

Beef 1,996,830

Butter „ 82,504

Cheese 639,386

Cocoa lb«. 3.763.275

Corn and Flour ... cwt 44,705,116

Currants „ 457.574

Egjgs gt. hund.

Farinaceous substances j^

Fkh

Fruit

Hams

Urd

MUk. condensed

Mutton

Oil, seed cake

Onions

Pork

P«»tatoes
Raisins

Rice

Pepper
Spirits

Sugar

Vegetables, raw
Wine

METALS.

Copper

Iron

Lead

P>'rltes
Quicksilver ...

Tin

Zinc

cwt.
cwt.

bush.
. cwL

lbs.
gaU.
cwt.

gall.

tons

667.687
27*170

602,00t

1.853.684

i.347.5«2

909.107

55.133

884.450

116.596

^ 1.701,378

393.132

262,444

234.*>oi

1.929.165

760.228

1.957.065

7.510.677

209,219

2,?;5.547

68,300

87.899

23.240

178620

lbs. 36.185

tons 19,860

.. 13.061

RAW MATERIALS.

Caoutchouc cwt.

Cotton, raw ,

Hides ,

Leather ,

Manures tons

OiU cocoanut & palm. cwt.

Paper ,

Paraffin gall.

Petroleum

Skins No.

Tallow cwt.

Tobacco lbs.

Wood loads

Wool, sheep's ... lbs.

MISCELLANEOUS.

Animals, living ... No.

Cork, manufactured lbs.

Glass manufactures cwt.

Jute ,. £

Rosin cwt.

382.947
16.184.362
220476
325.837
85.677
948,119
241,280
188.578

33.565.369
6.724,212
621,516
49,284,906
719.550
90.672.043

547.398

2,207,615

66,041

1.043.215

373.021

2,338.541
166,334
556,979

9.993.140
49.073.980
532.938
606,785
372,265
627,728

2.017,264

1.355.374

934.196

56.509

848,273

134.862

2.242,557
388.142

173.839
249,460

2.577.339
558.786

1.788.81 1

6.559,3<:2
211.469

2,800.626

70,301
128,091

24.949

204.243

6,coo

27.547

10.826

336,340

11,855,495

297,230

368.873

135.672

1,061,606

245.945

224,036

32.490.846

7.591.634

598.643
74.307,882

797.846
77,694,198

533.070

2,289,300

71.624

1.102,999

f^77.8il

YEAR.

Goods. 1898.

YARNS AND TEXTILE FABRICS.

1899.

Cotton yarn

lbs.

84.967,200

72,738,400

Cotton

manufactures

yds.

3,511,282,600 3.640,632,700

Jute yarn

lbs.

7,839.000

7,061,900

„ manufactures

yds.

32,287,800

31,827.500

Linen yarn

lbs.

3,472,900

4.239.900

„ manufactures

yds.

80,497.200

102,030.000

Woollen yarn

lbs.

1,536.400

1.734.600

Woollen

manufactures

yds.

64.284,600

66,814.900

METALS.

Brass

cwt.

36,331

32,838

Copper

„

253.964

272,066

Iron

tons

736.533

782.072

Lead

„

2.244

1.959

Tin

cwt.

31.279

33390

Zinc

„

24.619

20,577

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